Unify the three places that patch font loading for PDFium on Windows.

This also removed the code from content, which doesn't belong there because it's for a feature in Chrome.

In order to implement this in a unified way, I needed to create a public interface around ChildThread. A lot of the change is updating callers of ChildThread to use ChildThreadImpl instead.

BUG=448473

Review URL: https://codereview.chromium.org/897563002

Cr-Commit-Position: refs/heads/master@{#314367}

64 files changed, 330 insertions, 354 deletions

diff --git a/content/app/android/child_process_service.cc b/content/app/android/child_process_service.cc
index 9d46e08..93c622e 100644
--- a/content/app/android/child_process_service.cc
+++ b/content/app/android/child_process_service.cc
@@ -12,7 +12,7 @@
 #include "base/android/memory_pressure_listener_android.h"
 #include "base/logging.h"
 #include "base/posix/global_descriptors.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/android/surface_texture_manager.h"
 #include "content/common/android/surface_texture_peer.h"
 #include "content/common/gpu/gpu_surface_lookup.h"
@@ -188,7 +188,7 @@ bool RegisterChildProcessService(JNIEnv* env) {
 }
 
 void ShutdownMainThread(JNIEnv* env, jobject obj) {
-  ChildThread::ShutdownThread();
+  ChildThreadImpl::ShutdownThread();
 }
 
 }  // namespace content
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index d5b5367..a8d488a 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -31,7 +31,7 @@
 #include "content/app/resources/grit/content_resources.h"
 #include "content/app/strings/grit/content_strings.h"
 #include "content/child/bluetooth/web_bluetooth_impl.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/content_child_helpers.h"
 #include "content/child/geofencing/web_geofencing_provider_impl.h"
 #include "content/child/navigator_connect/navigator_connect_provider.h"
@@ -436,15 +436,15 @@ BlinkPlatformImpl::BlinkPlatformImpl(
 
 void BlinkPlatformImpl::InternalInit() {
   // ChildThread may not exist in some tests.
-  if (ChildThread::current()) {
+  if (ChildThreadImpl::current()) {
     geofencing_provider_.reset(new WebGeofencingProviderImpl(
-        ChildThread::current()->thread_safe_sender()));
+        ChildThreadImpl::current()->thread_safe_sender()));
     bluetooth_.reset(
-        new WebBluetoothImpl(ChildThread::current()->thread_safe_sender()));
-    thread_safe_sender_ = ChildThread::current()->thread_safe_sender();
+        new WebBluetoothImpl(ChildThreadImpl::current()->thread_safe_sender()));
+    thread_safe_sender_ = ChildThreadImpl::current()->thread_safe_sender();
     notification_dispatcher_ =
-        ChildThread::current()->notification_dispatcher();
-    push_dispatcher_ = ChildThread::current()->push_dispatcher();
+        ChildThreadImpl::current()->notification_dispatcher();
+    push_dispatcher_ = ChildThreadImpl::current()->push_dispatcher();
   }
 
   if (main_thread_task_runner_.get()) {
@@ -456,7 +456,7 @@ BlinkPlatformImpl::~BlinkPlatformImpl() {
 }
 
 WebURLLoader* BlinkPlatformImpl::createURLLoader() {
-  ChildThread* child_thread = ChildThread::current();
+  ChildThreadImpl* child_thread = ChildThreadImpl::current();
   // There may be no child thread in RenderViewTests.  These tests can still use
   // data URLs to bypass the ResourceDispatcher.
   return new WebURLLoaderImpl(
diff --git a/content/child/child_discardable_shared_memory_manager.cc b/content/child/child_discardable_shared_memory_manager.cc
index 7d07e32..83d29d6 100644
--- a/content/child/child_discardable_shared_memory_manager.cc
+++ b/content/child/child_discardable_shared_memory_manager.cc
@@ -6,7 +6,6 @@
 
 #include "base/memory/discardable_shared_memory.h"
 #include "base/process/process_metrics.h"
-#include "content/child/child_thread.h"
 #include "content/common/child_process_messages.h"
 
 namespace content {
diff --git a/content/child/child_gpu_memory_buffer_manager.cc b/content/child/child_gpu_memory_buffer_manager.cc
index 7cb793d..0e1c312 100644
--- a/content/child/child_gpu_memory_buffer_manager.cc
+++ b/content/child/child_gpu_memory_buffer_manager.cc
@@ -4,7 +4,6 @@
 
 #include "content/child/child_gpu_memory_buffer_manager.h"
 
-#include "content/child/child_thread.h"
 #include "content/common/child_process_messages.h"
 #include "content/common/gpu/client/gpu_memory_buffer_impl.h"
 
diff --git a/content/child/child_histogram_message_filter.cc b/content/child/child_histogram_message_filter.cc
index 3e895fc..3e778d5 100644
--- a/content/child/child_histogram_message_filter.cc
+++ b/content/child/child_histogram_message_filter.cc
@@ -10,7 +10,6 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram_delta_serialization.h"
 #include "content/child/child_process.h"
-#include "content/child/child_thread.h"
 #include "content/common/child_process_messages.h"
 #include "ipc/ipc_sender.h"
 
diff --git a/content/child/child_message_filter.cc b/content/child/child_message_filter.cc
index 9e5ff63..66b7555 100644
--- a/content/child/child_message_filter.cc
+++ b/content/child/child_message_filter.cc
@@ -8,7 +8,7 @@
 #include "base/bind_helpers.h"
 #include "base/location.h"
 #include "base/task_runner.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/thread_safe_sender.h"
 #include "ipc/message_filter.h"
 
@@ -52,7 +52,7 @@ base::TaskRunner* ChildMessageFilter::OverrideTaskRunnerForMessage(
 
 ChildMessageFilter::ChildMessageFilter()
     : internal_(NULL),
-      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {}
+      thread_safe_sender_(ChildThreadImpl::current()->thread_safe_sender()) {}
 
 ChildMessageFilter::~ChildMessageFilter() {}
 
diff --git a/content/child/child_message_filter.h b/content/child/child_message_filter.h
index a79ceec..e3dbdf8 100644
--- a/content/child/child_message_filter.h
+++ b/content/child/child_message_filter.h
@@ -51,7 +51,7 @@ class ChildMessageFilter
 
  private:
   class Internal;
-  friend class ChildThread;
+  friend class ChildThreadImpl;
   friend class RenderThreadImpl;
   friend class WorkerThread;
 
diff --git a/content/child/child_process.cc b/content/child/child_process.cc
index 42eff93..db73ea3 100644
--- a/content/child/child_process.cc
+++ b/content/child/child_process.cc
@@ -16,7 +16,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/threading/thread.h"
 #include "base/threading/thread_local.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 
 #if defined(OS_ANDROID)
 #include "base/debug/debugger.h"
@@ -72,11 +72,11 @@ ChildProcess::~ChildProcess() {
   io_thread_.Stop();
 }
 
-ChildThread* ChildProcess::main_thread() {
+ChildThreadImpl* ChildProcess::main_thread() {
   return main_thread_.get();
 }
 
-void ChildProcess::set_main_thread(ChildThread* thread) {
+void ChildProcess::set_main_thread(ChildThreadImpl* thread) {
   main_thread_.reset(thread);
 }
 
diff --git a/content/child/child_process.h b/content/child/child_process.h
index 1aedcb6..cf3173f 100644
--- a/content/child/child_process.h
+++ b/content/child/child_process.h
@@ -12,7 +12,7 @@
 #include "content/common/content_export.h"
 
 namespace content {
-class ChildThread;
+class ChildThreadImpl;
 
 // Base class for child processes of the browser process (i.e. renderer and
 // plugin host). This is a singleton object for each child process.
@@ -22,12 +22,12 @@ class ChildThread;
 //
 // 1. ChildProcess::~ChildProcess() is called.
 //   2. Shutdown event is fired. Background threads should stop.
-//   3. ChildThread::Shutdown() is called. ChildThread is also deleted.
+//   3. ChildThreadImpl::Shutdown() is called. ChildThread is also deleted.
 //   4. IO thread is stopped.
 // 5. Main message loop exits.
 // 6. Child process is now fully stopped.
 //
-// Note: IO thread outlives the ChildThread object.
+// Note: IO thread outlives the ChildThreadImpl object.
 class CONTENT_EXPORT ChildProcess {
  public:
   // Child processes should have an object that derives from this class.
@@ -36,11 +36,11 @@ class CONTENT_EXPORT ChildProcess {
   virtual ~ChildProcess();
 
   // May be NULL if the main thread hasn't been set explicitly.
-  ChildThread* main_thread();
+  ChildThreadImpl* main_thread();
 
   // Sets the object associated with the main thread of this process.
   // Takes ownership of the pointer.
-  void set_main_thread(ChildThread* thread);
+  void set_main_thread(ChildThreadImpl* thread);
 
   base::MessageLoop* io_message_loop() { return io_thread_.message_loop(); }
   base::MessageLoopProxy* io_message_loop_proxy() {
@@ -81,7 +81,7 @@ class CONTENT_EXPORT ChildProcess {
   // NOTE: make sure that main_thread_ is listed after shutdown_event_, since
   // it depends on it (indirectly through IPC::SyncChannel).  Same for
   // io_thread_.
-  scoped_ptr<ChildThread> main_thread_;
+  scoped_ptr<ChildThreadImpl> main_thread_;
 
   DISALLOW_COPY_AND_ASSIGN(ChildProcess);
 };
diff --git a/content/child/child_shared_bitmap_manager.cc b/content/child/child_shared_bitmap_manager.cc
index 5cccb6d36..73395da 100644
--- a/content/child/child_shared_bitmap_manager.cc
+++ b/content/child/child_shared_bitmap_manager.cc
@@ -6,7 +6,7 @@
 
 #include "base/debug/alias.h"
 #include "base/process/process_metrics.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/child_process_messages.h"
 #include "ui/gfx/geometry/size.h"
 
@@ -111,7 +111,7 @@ ChildSharedBitmapManager::AllocateSharedMemoryBitmap(const gfx::Size& size) {
   if (!memory->Map(memory_size))
     CHECK(false);
 #else
-  memory = ChildThread::AllocateSharedMemory(memory_size, sender_.get());
+  memory = ChildThreadImpl::AllocateSharedMemory(memory_size, sender_.get());
 #if defined(OS_WIN)
   if (!memory)
     CollectMemoryUsageAndDie(size);
diff --git a/content/child/child_thread.cc b/content/child/child_thread_impl.cc
index 82caa77..4db2e27 100644
--- a/content/child/child_thread.cc
+++ b/content/child/child_thread_impl.cc
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 
 #include <signal.h>
 
@@ -71,7 +71,7 @@ namespace {
 // How long to wait for a connection to the browser process before giving up.
 const int kConnectionTimeoutS = 15;
 
-base::LazyInstance<base::ThreadLocalPointer<ChildThread> > g_lazy_tls =
+base::LazyInstance<base::ThreadLocalPointer<ChildThreadImpl> > g_lazy_tls =
     LAZY_INSTANCE_INITIALIZER;
 
 // This isn't needed on Windows because there the sandbox's job object
@@ -162,7 +162,7 @@ class SuicideOnChannelErrorFilter : public IPC::MessageFilter {
 #endif  // OS(POSIX)
 
 #if defined(OS_ANDROID)
-ChildThread* g_child_thread = NULL;
+ChildThreadImpl* g_child_thread = NULL;
 
 // A lock protects g_child_thread.
 base::LazyInstance<base::Lock> g_lazy_child_thread_lock =
@@ -199,50 +199,54 @@ void QuitMainThreadMessageLoop() {
 
 }  // namespace
 
-ChildThread::Options::Options()
+ChildThread* ChildThread::Get() {
+  return ChildThreadImpl::current();
+}
+
+ChildThreadImpl::Options::Options()
     : channel_name(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kProcessChannelID)),
       use_mojo_channel(false),
       in_browser_process(false) {
 }
 
-ChildThread::Options::Options(bool mojo)
+ChildThreadImpl::Options::Options(bool mojo)
     : channel_name(base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
           switches::kProcessChannelID)),
       use_mojo_channel(mojo),
       in_browser_process(true) {
 }
 
-ChildThread::Options::Options(std::string name, bool mojo)
+ChildThreadImpl::Options::Options(std::string name, bool mojo)
     : channel_name(name), use_mojo_channel(mojo), in_browser_process(true) {
 }
 
-ChildThread::Options::~Options() {
+ChildThreadImpl::Options::~Options() {
 }
 
-ChildThread::ChildThreadMessageRouter::ChildThreadMessageRouter(
+ChildThreadImpl::ChildThreadMessageRouter::ChildThreadMessageRouter(
     IPC::Sender* sender)
     : sender_(sender) {}
 
-bool ChildThread::ChildThreadMessageRouter::Send(IPC::Message* msg) {
+bool ChildThreadImpl::ChildThreadMessageRouter::Send(IPC::Message* msg) {
   return sender_->Send(msg);
 }
 
-ChildThread::ChildThread()
+ChildThreadImpl::ChildThreadImpl()
     : router_(this),
       in_browser_process_(false),
       channel_connected_factory_(this) {
   Init(Options());
 }
 
-ChildThread::ChildThread(const Options& options)
+ChildThreadImpl::ChildThreadImpl(const Options& options)
     : router_(this),
       in_browser_process_(options.in_browser_process),
       channel_connected_factory_(this) {
   Init(options);
 }
 
-void ChildThread::ConnectChannel(bool use_mojo_channel) {
+void ChildThreadImpl::ConnectChannel(bool use_mojo_channel) {
   bool create_pipe_now = true;
   if (use_mojo_channel) {
     VLOG(1) << "Mojo is enabled on child";
@@ -255,7 +259,7 @@ void ChildThread::ConnectChannel(bool use_mojo_channel) {
   channel_->Init(channel_name_, IPC::Channel::MODE_CLIENT, create_pipe_now);
 }
 
-void ChildThread::Init(const Options& options) {
+void ChildThreadImpl::Init(const Options& options) {
   channel_name_ = options.channel_name;
 
   g_lazy_tls.Pointer()->Set(this);
@@ -363,7 +367,7 @@ void ChildThread::Init(const Options& options) {
 
   base::MessageLoop::current()->PostDelayedTask(
       FROM_HERE,
-      base::Bind(&ChildThread::EnsureConnected,
+      base::Bind(&ChildThreadImpl::EnsureConnected,
                  channel_connected_factory_.GetWeakPtr()),
       base::TimeDelta::FromSeconds(connection_timeout));
 
@@ -395,7 +399,7 @@ void ChildThread::Init(const Options& options) {
       new ChildDiscardableSharedMemoryManager(thread_safe_sender()));
 }
 
-ChildThread::~ChildThread() {
+ChildThreadImpl::~ChildThreadImpl() {
 #ifdef IPC_MESSAGE_LOG_ENABLED
   IPC::Logging::GetInstance()->SetIPCSender(NULL);
 #endif
@@ -415,7 +419,7 @@ ChildThread::~ChildThread() {
   g_lazy_tls.Pointer()->Set(NULL);
 }
 
-void ChildThread::Shutdown() {
+void ChildThreadImpl::Shutdown() {
   // Delete objects that hold references to blink so derived classes can
   // safely shutdown blink in their Shutdown implementation.
   file_system_dispatcher_.reset();
@@ -423,16 +427,16 @@ void ChildThread::Shutdown() {
   WebFileSystemImpl::DeleteThreadSpecificInstance();
 }
 
-void ChildThread::OnChannelConnected(int32 peer_pid) {
+void ChildThreadImpl::OnChannelConnected(int32 peer_pid) {
   channel_connected_factory_.InvalidateWeakPtrs();
 }
 
-void ChildThread::OnChannelError() {
+void ChildThreadImpl::OnChannelError() {
   set_on_channel_error_called(true);
   base::MessageLoop::current()->Quit();
 }
 
-bool ChildThread::Send(IPC::Message* msg) {
+bool ChildThreadImpl::Send(IPC::Message* msg) {
   DCHECK(base::MessageLoop::current() == message_loop());
   if (!channel_) {
     delete msg;
@@ -442,19 +446,29 @@ bool ChildThread::Send(IPC::Message* msg) {
   return channel_->Send(msg);
 }
 
-MessageRouter* ChildThread::GetRouter() {
+#if defined(OS_WIN)
+void ChildThreadImpl::PreCacheFont(const LOGFONT& log_font) {
+  Send(new ChildProcessHostMsg_PreCacheFont(log_font));
+}
+
+void ChildThreadImpl::ReleaseCachedFonts() {
+  Send(new ChildProcessHostMsg_ReleaseCachedFonts());
+}
+#endif
+
+MessageRouter* ChildThreadImpl::GetRouter() {
   DCHECK(base::MessageLoop::current() == message_loop());
   return &router_;
 }
 
-scoped_ptr<base::SharedMemory> ChildThread::AllocateSharedMemory(
+scoped_ptr<base::SharedMemory> ChildThreadImpl::AllocateSharedMemory(
     size_t buf_size) {
   DCHECK(base::MessageLoop::current() == message_loop());
   return AllocateSharedMemory(buf_size, this);
 }
 
 // static
-scoped_ptr<base::SharedMemory> ChildThread::AllocateSharedMemory(
+scoped_ptr<base::SharedMemory> ChildThreadImpl::AllocateSharedMemory(
     size_t buf_size,
     IPC::Sender* sender) {
   scoped_ptr<base::SharedMemory> shared_buf;
@@ -484,7 +498,7 @@ scoped_ptr<base::SharedMemory> ChildThread::AllocateSharedMemory(
   return shared_buf;
 }
 
-bool ChildThread::OnMessageReceived(const IPC::Message& msg) {
+bool ChildThreadImpl::OnMessageReceived(const IPC::Message& msg) {
   if (mojo_application_->OnMessageReceived(msg))
     return true;
 
@@ -497,7 +511,7 @@ bool ChildThread::OnMessageReceived(const IPC::Message& msg) {
     return true;
 
   bool handled = true;
-  IPC_BEGIN_MESSAGE_MAP(ChildThread, msg)
+  IPC_BEGIN_MESSAGE_MAP(ChildThreadImpl, msg)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_Shutdown, OnShutdown)
 #if defined(IPC_MESSAGE_LOG_ENABLED)
     IPC_MESSAGE_HANDLER(ChildProcessMsg_SetIPCLoggingEnabled,
@@ -525,16 +539,16 @@ bool ChildThread::OnMessageReceived(const IPC::Message& msg) {
   return router_.OnMessageReceived(msg);
 }
 
-bool ChildThread::OnControlMessageReceived(const IPC::Message& msg) {
+bool ChildThreadImpl::OnControlMessageReceived(const IPC::Message& msg) {
   return false;
 }
 
-void ChildThread::OnShutdown() {
+void ChildThreadImpl::OnShutdown() {
   base::MessageLoop::current()->Quit();
 }
 
 #if defined(IPC_MESSAGE_LOG_ENABLED)
-void ChildThread::OnSetIPCLoggingEnabled(bool enable) {
+void ChildThreadImpl::OnSetIPCLoggingEnabled(bool enable) {
   if (enable)
     IPC::Logging::GetInstance()->Enable();
   else
@@ -542,11 +556,11 @@ void ChildThread::OnSetIPCLoggingEnabled(bool enable) {
 }
 #endif  //  IPC_MESSAGE_LOG_ENABLED
 
-void ChildThread::OnSetProfilerStatus(ThreadData::Status status) {
+void ChildThreadImpl::OnSetProfilerStatus(ThreadData::Status status) {
   ThreadData::InitializeAndSetTrackingStatus(status);
 }
 
-void ChildThread::OnGetChildProfilerData(int sequence_number) {
+void ChildThreadImpl::OnGetChildProfilerData(int sequence_number) {
   tracked_objects::ProcessDataSnapshot process_data;
   ThreadData::Snapshot(false, &process_data);
 
@@ -554,7 +568,7 @@ void ChildThread::OnGetChildProfilerData(int sequence_number) {
                                                  process_data));
 }
 
-void ChildThread::OnDumpHandles() {
+void ChildThreadImpl::OnDumpHandles() {
 #if defined(OS_WIN)
   scoped_refptr<HandleEnumerator> handle_enum(
       new HandleEnumerator(
@@ -568,7 +582,7 @@ void ChildThread::OnDumpHandles() {
 }
 
 #if defined(USE_TCMALLOC)
-void ChildThread::OnGetTcmallocStats() {
+void ChildThreadImpl::OnGetTcmallocStats() {
   std::string result;
   char buffer[1024 * 32];
   base::allocator::GetStats(buffer, sizeof(buffer));
@@ -577,15 +591,15 @@ void ChildThread::OnGetTcmallocStats() {
 }
 #endif
 
-ChildThread* ChildThread::current() {
+ChildThreadImpl* ChildThreadImpl::current() {
   return g_lazy_tls.Pointer()->Get();
 }
 
 #if defined(OS_ANDROID)
 // The method must NOT be called on the child thread itself.
 // It may block the child thread if so.
-void ChildThread::ShutdownThread() {
-  DCHECK(!ChildThread::current()) <<
+void ChildThreadImpl::ShutdownThread() {
+  DCHECK(!ChildThreadImpl::current()) <<
       "this method should NOT be called from child thread itself";
   {
     base::AutoLock lock(g_lazy_child_thread_lock.Get());
@@ -598,7 +612,7 @@ void ChildThread::ShutdownThread() {
 }
 #endif
 
-void ChildThread::OnProcessFinalRelease() {
+void ChildThreadImpl::OnProcessFinalRelease() {
   if (on_channel_error_called_) {
     base::MessageLoop::current()->Quit();
     return;
@@ -613,12 +627,12 @@ void ChildThread::OnProcessFinalRelease() {
   Send(new ChildProcessHostMsg_ShutdownRequest);
 }
 
-void ChildThread::EnsureConnected() {
-  VLOG(0) << "ChildThread::EnsureConnected()";
+void ChildThreadImpl::EnsureConnected() {
+  VLOG(0) << "ChildThreadImpl::EnsureConnected()";
   base::KillProcess(base::GetCurrentProcessHandle(), 0, false);
 }
 
-void ChildThread::OnProcessBackgrounded(bool background) {
+void ChildThreadImpl::OnProcessBackgrounded(bool background) {
   // Set timer slack to maximum on main thread when in background.
   base::TimerSlack timer_slack = base::TIMER_SLACK_NONE;
   if (background)
diff --git a/content/child/child_thread.h b/content/child/child_thread_impl.h
index 24cfc61..e4f5c3f 100644
--- a/content/child/child_thread.h
+++ b/content/child/child_thread_impl.h
@@ -2,8 +2,8 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#ifndef CONTENT_CHILD_CHILD_THREAD_H_
-#define CONTENT_CHILD_CHILD_THREAD_H_
+#ifndef CONTENT_CHILD_CHILD_THREAD_IMPL_H_
+#define CONTENT_CHILD_CHILD_THREAD_IMPL_H_
 
 #include <string>
 
@@ -16,6 +16,7 @@
 #include "content/child/mojo/mojo_application.h"
 #include "content/common/content_export.h"
 #include "content/common/message_router.h"
+#include "content/public/child/child_thread.h"
 #include "ipc/ipc_message.h"  // For IPC_MESSAGE_LOG_ENABLED.
 
 namespace base {
@@ -57,7 +58,9 @@ class WebSocketDispatcher;
 struct RequestInfo;
 
 // The main thread of a child process derives from this class.
-class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
+class CONTENT_EXPORT ChildThreadImpl
+    : public IPC::Listener,
+      virtual public ChildThread {
  public:
   struct CONTENT_EXPORT Options {
     Options();
@@ -72,21 +75,27 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
   };
 
   // Creates the thread.
-  ChildThread();
+  ChildThreadImpl();
   // Allow to be used for single-process mode and for in process gpu mode via
   // options.
-  explicit ChildThread(const Options& options);
+  explicit ChildThreadImpl(const Options& options);
   // ChildProcess::main_thread() is reset after Shutdown(), and before the
   // destructor, so any subsystem that relies on ChildProcess::main_thread()
   // must be terminated before Shutdown returns. In particular, if a subsystem
   // has a thread that post tasks to ChildProcess::main_thread(), that thread
   // should be joined in Shutdown().
-  ~ChildThread() override;
+  ~ChildThreadImpl() override;
   virtual void Shutdown();
 
   // IPC::Sender implementation:
   bool Send(IPC::Message* msg) override;
 
+  // ChildThread implementation:
+#if defined(OS_WIN)
+  void PreCacheFont(const LOGFONT& log_font) override;
+  void ReleaseCachedFonts() override;
+#endif
+
   IPC::SyncChannel* channel() { return channel_.get(); }
 
   MessageRouter* GetRouter();
@@ -170,7 +179,7 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
   base::MessageLoop* message_loop() const { return message_loop_; }
 
   // Returns the one child thread. Can only be called on the main thread.
-  static ChildThread* current();
+  static ChildThreadImpl* current();
 
 #if defined(OS_ANDROID)
   // Called on Android's service thread to shutdown the main thread of this
@@ -241,7 +250,8 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
 
   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
 
-  // Implements message routing functionality to the consumers of ChildThread.
+  // Implements message routing functionality to the consumers of
+  // ChildThreadImpl.
   ChildThreadMessageRouter router_;
 
   // Handles resource loads for this process.
@@ -292,11 +302,11 @@ class CONTENT_EXPORT ChildThread : public IPC::Listener, public IPC::Sender {
 
   bool in_browser_process_;
 
-  base::WeakPtrFactory<ChildThread> channel_connected_factory_;
+  base::WeakPtrFactory<ChildThreadImpl> channel_connected_factory_;
 
-  DISALLOW_COPY_AND_ASSIGN(ChildThread);
+  DISALLOW_COPY_AND_ASSIGN(ChildThreadImpl);
 };
 
 }  // namespace content
 
-#endif  // CONTENT_CHILD_CHILD_THREAD_H_
+#endif  // CONTENT_CHILD_CHILD_THREAD_IMPL_H_
diff --git a/content/child/fileapi/file_system_dispatcher.cc b/content/child/fileapi/file_system_dispatcher.cc
index 8ba8764..1a742db 100644
--- a/content/child/fileapi/file_system_dispatcher.cc
+++ b/content/child/fileapi/file_system_dispatcher.cc
@@ -8,7 +8,7 @@
 #include "base/files/file_util.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/process/process.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/fileapi/file_system_messages.h"
 #include "storage/common/fileapi/file_system_info.h"
 
@@ -171,7 +171,7 @@ void FileSystemDispatcher::OpenFileSystem(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_OpenFileSystem(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_OpenFileSystem(
       request_id, origin_url, type));
 }
 
@@ -181,7 +181,7 @@ void FileSystemDispatcher::ResolveURL(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_ResolveURL(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_ResolveURL(
           request_id, filesystem_url));
 }
 
@@ -189,7 +189,7 @@ void FileSystemDispatcher::DeleteFileSystem(const GURL& origin_url,
                                             storage::FileSystemType type,
                                             const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_DeleteFileSystem(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_DeleteFileSystem(
           request_id, origin_url, type));
 }
 
@@ -198,7 +198,7 @@ void FileSystemDispatcher::Move(
     const GURL& dest_path,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_Move(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_Move(
           request_id, src_path, dest_path));
 }
 
@@ -207,7 +207,7 @@ void FileSystemDispatcher::Copy(
     const GURL& dest_path,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_Copy(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_Copy(
       request_id, src_path, dest_path));
 }
 
@@ -216,7 +216,7 @@ void FileSystemDispatcher::Remove(
     bool recursive,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_Remove(request_id, path, recursive));
 }
 
@@ -226,7 +226,7 @@ void FileSystemDispatcher::ReadMetadata(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_ReadMetadata(request_id, path));
 }
 
@@ -235,7 +235,7 @@ void FileSystemDispatcher::CreateFile(
     bool exclusive,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_Create(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_Create(
       request_id, path, exclusive,
       false /* is_directory */, false /* recursive */));
 }
@@ -246,7 +246,7 @@ void FileSystemDispatcher::CreateDirectory(
     bool recursive,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_Create(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_Create(
       request_id, path, exclusive, true /* is_directory */, recursive));
 }
 
@@ -255,7 +255,7 @@ void FileSystemDispatcher::Exists(
     bool is_directory,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_Exists(request_id, path, is_directory));
 }
 
@@ -265,7 +265,7 @@ void FileSystemDispatcher::ReadDirectory(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_ReadDirectory(request_id, path));
 }
 
@@ -275,7 +275,7 @@ void FileSystemDispatcher::Truncate(
     int* request_id_out,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_Truncate(request_id, path, offset));
 
   if (request_id_out)
@@ -291,7 +291,7 @@ void FileSystemDispatcher::Write(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_Write(request_id, path, blob_id, offset));
 
   if (request_id_out)
@@ -302,7 +302,7 @@ void FileSystemDispatcher::Cancel(
     int request_id_to_cancel,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(new FileSystemHostMsg_CancelWrite(
+  ChildThreadImpl::current()->Send(new FileSystemHostMsg_CancelWrite(
       request_id, request_id_to_cancel));
 }
 
@@ -312,7 +312,7 @@ void FileSystemDispatcher::TouchFile(
     const base::Time& last_modified_time,
     const StatusCallback& callback) {
   int request_id = dispatchers_.Add(CallbackDispatcher::Create(callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_TouchFile(
           request_id, path, last_access_time, last_modified_time));
 }
@@ -323,7 +323,7 @@ void FileSystemDispatcher::CreateSnapshotFile(
     const StatusCallback& error_callback) {
   int request_id = dispatchers_.Add(
       CallbackDispatcher::Create(success_callback, error_callback));
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new FileSystemHostMsg_CreateSnapshotFile(
           request_id, file_path));
 }
diff --git a/content/child/fileapi/webfilesystem_impl.cc b/content/child/fileapi/webfilesystem_impl.cc
index 8fe0243..f41377f 100644
--- a/content/child/fileapi/webfilesystem_impl.cc
+++ b/content/child/fileapi/webfilesystem_impl.cc
@@ -11,7 +11,7 @@
 #include "base/strings/utf_string_conversions.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/threading/thread_local.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/file_info_util.h"
 #include "content/child/fileapi/file_system_dispatcher.h"
 #include "content/child/fileapi/webfilewriter_impl.h"
@@ -86,8 +86,8 @@ base::LazyInstance<base::ThreadLocalPointer<WebFileSystemImpl> >::Leaky
     g_webfilesystem_tls = LAZY_INSTANCE_INITIALIZER;
 
 void DidReceiveSnapshotFile(int request_id) {
-  if (ChildThread::current())
-    ChildThread::current()->Send(
+  if (ChildThreadImpl::current())
+    ChildThreadImpl::current()->Send(
         new FileSystemHostMsg_DidReceiveSnapshotFile(request_id));
 }
 
@@ -110,12 +110,12 @@ void CallDispatcherOnMainThread(
       return;
     waitable_results->WaitAndRun();
   }
-  if (!ChildThread::current() ||
-      !ChildThread::current()->file_system_dispatcher())
+  if (!ChildThreadImpl::current() ||
+      !ChildThreadImpl::current()->file_system_dispatcher())
     return;
 
   DCHECK(!waitable_results);
-  DispatchToMethod(ChildThread::current()->file_system_dispatcher(),
+  DispatchToMethod(ChildThreadImpl::current()->file_system_dispatcher(),
                    method, params);
 }
 
diff --git a/content/child/fileapi/webfilewriter_impl.cc b/content/child/fileapi/webfilewriter_impl.cc
index a8fd3ea..0af17b8 100644
--- a/content/child/fileapi/webfilewriter_impl.cc
+++ b/content/child/fileapi/webfilewriter_impl.cc
@@ -6,7 +6,7 @@
 
 #include "base/bind.h"
 #include "base/synchronization/waitable_event.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/fileapi/file_system_dispatcher.h"
 #include "content/child/worker_task_runner.h"
 
@@ -15,8 +15,8 @@ namespace content {
 namespace {
 
 FileSystemDispatcher* GetFileSystemDispatcher() {
-  return ChildThread::current() ?
-      ChildThread::current()->file_system_dispatcher() : NULL;
+  return ChildThreadImpl::current() ?
+      ChildThreadImpl::current()->file_system_dispatcher() : NULL;
 }
 
 }  // namespace
@@ -42,7 +42,7 @@ class WebFileWriterImpl::WriterBridge
     status_callback_ = status_callback;
     if (!GetFileSystemDispatcher())
       return;
-    ChildThread::current()->file_system_dispatcher()->Truncate(
+    ChildThreadImpl::current()->file_system_dispatcher()->Truncate(
         path, offset, &request_id_,
         base::Bind(&WriterBridge::DidFinish, this));
   }
@@ -54,7 +54,7 @@ class WebFileWriterImpl::WriterBridge
     status_callback_ = error_callback;
     if (!GetFileSystemDispatcher())
       return;
-    ChildThread::current()->file_system_dispatcher()->Write(
+    ChildThreadImpl::current()->file_system_dispatcher()->Write(
         path, id, offset, &request_id_,
         base::Bind(&WriterBridge::DidWrite, this),
         base::Bind(&WriterBridge::DidFinish, this));
@@ -64,7 +64,7 @@ class WebFileWriterImpl::WriterBridge
     status_callback_ = status_callback;
     if (!GetFileSystemDispatcher())
       return;
-    ChildThread::current()->file_system_dispatcher()->Cancel(
+    ChildThreadImpl::current()->file_system_dispatcher()->Cancel(
         request_id_,
         base::Bind(&WriterBridge::DidFinish, this));
   }
diff --git a/content/child/notifications/notification_image_loader.cc b/content/child/notifications/notification_image_loader.cc
index b2eb23e..c194b02 100644
--- a/content/child/notifications/notification_image_loader.cc
+++ b/content/child/notifications/notification_image_loader.cc
@@ -5,7 +5,7 @@
 #include "content/child/notifications/notification_image_loader.h"
 
 #include "base/logging.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/image_decoder.h"
 #include "content/child/worker_task_runner.h"
 #include "third_party/WebKit/public/platform/Platform.h"
@@ -29,7 +29,7 @@ NotificationImageLoader::~NotificationImageLoader() {}
 
 void NotificationImageLoader::StartOnMainThread(const WebURL& image_url,
                                                 int worker_thread_id) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   DCHECK(!url_loader_);
 
   worker_thread_id_ = worker_thread_id;
diff --git a/content/child/npapi/plugin_url_fetcher.cc b/content/child/npapi/plugin_url_fetcher.cc
index c7db56c..15bd602 100644
--- a/content/child/npapi/plugin_url_fetcher.cc
+++ b/content/child/npapi/plugin_url_fetcher.cc
@@ -5,7 +5,7 @@
 #include "content/child/npapi/plugin_url_fetcher.h"
 
 #include "base/memory/scoped_ptr.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/multipart_response_delegate.h"
 #include "content/child/npapi/plugin_host.h"
 #include "content/child/npapi/plugin_instance.h"
@@ -146,7 +146,7 @@ PluginURLFetcher::PluginURLFetcher(PluginStreamUrl* plugin_stream,
       request_info.headers = std::string("Range: ") + range;
   }
 
-  bridge_.reset(ChildThread::current()->resource_dispatcher()->CreateBridge(
+  bridge_.reset(ChildThreadImpl::current()->resource_dispatcher()->CreateBridge(
       request_info));
   if (!body.empty()) {
     scoped_refptr<ResourceRequestBody> request_body =
diff --git a/content/child/quota_dispatcher.cc b/content/child/quota_dispatcher.cc
index 1a1577a..fa766db 100644
--- a/content/child/quota_dispatcher.cc
+++ b/content/child/quota_dispatcher.cc
@@ -7,7 +7,6 @@
 #include "base/basictypes.h"
 #include "base/lazy_instance.h"
 #include "base/threading/thread_local.h"
-#include "content/child/child_thread.h"
 #include "content/child/quota_message_filter.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/common/quota_messages.h"
diff --git a/content/child/resource_dispatcher.cc b/content/child/resource_dispatcher.cc
index ba7fe6f..bccff3b 100644
--- a/content/child/resource_dispatcher.cc
+++ b/content/child/resource_dispatcher.cc
@@ -16,7 +16,6 @@
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/strings/string_util.h"
-#include "content/child/child_thread.h"
 #include "content/child/request_extra_data.h"
 #include "content/child/request_info.h"
 #include "content/child/resource_loader_bridge.h"
diff --git a/content/child/service_worker/service_worker_dispatcher.cc b/content/child/service_worker/service_worker_dispatcher.cc
index fce8783..99230db 100644
--- a/content/child/service_worker/service_worker_dispatcher.cc
+++ b/content/child/service_worker/service_worker_dispatcher.cc
@@ -8,7 +8,7 @@
 #include "base/stl_util.h"
 #include "base/threading/thread_local.h"
 #include "base/trace_event/trace_event.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/service_worker/service_worker_handle_reference.h"
 #include "content/child/service_worker/service_worker_provider_context.h"
 #include "content/child/service_worker/service_worker_registration_handle_reference.h"
@@ -638,7 +638,7 @@ void ServiceWorkerDispatcher::OnPostMessage(
     const std::vector<int>& new_routing_ids) {
   // Make sure we're on the main document thread. (That must be the only
   // thread we get this message)
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   TRACE_EVENT1("ServiceWorker",
                "ServiceWorkerDispatcher::OnPostMessage",
                "Thread ID", thread_id);
diff --git a/content/child/service_worker/service_worker_network_provider.cc b/content/child/service_worker/service_worker_network_provider.cc
index db09351..915a1c9 100644
--- a/content/child/service_worker/service_worker_network_provider.cc
+++ b/content/child/service_worker/service_worker_network_provider.cc
@@ -5,7 +5,7 @@
 #include "content/child/service_worker/service_worker_network_provider.h"
 
 #include "base/atomic_sequence_num.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/service_worker/service_worker_provider_context.h"
 #include "content/common/service_worker/service_worker_messages.h"
 
@@ -38,24 +38,24 @@ ServiceWorkerNetworkProvider* ServiceWorkerNetworkProvider::FromDocumentState(
 ServiceWorkerNetworkProvider::ServiceWorkerNetworkProvider(int render_frame_id)
     : provider_id_(GetNextProviderId()),
       context_(new ServiceWorkerProviderContext(provider_id_)) {
-  if (!ChildThread::current())
+  if (!ChildThreadImpl::current())
     return;  // May be null in some tests.
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new ServiceWorkerHostMsg_ProviderCreated(provider_id_, render_frame_id));
 }
 
 ServiceWorkerNetworkProvider::~ServiceWorkerNetworkProvider() {
-  if (!ChildThread::current())
+  if (!ChildThreadImpl::current())
     return;  // May be null in some tests.
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new ServiceWorkerHostMsg_ProviderDestroyed(provider_id_));
 }
 
 void ServiceWorkerNetworkProvider::SetServiceWorkerVersionId(
     int64 version_id) {
-  if (!ChildThread::current())
+  if (!ChildThreadImpl::current())
     return;  // May be null in some tests.
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new ServiceWorkerHostMsg_SetVersionId(provider_id_, version_id));
 }
 
diff --git a/content/child/service_worker/service_worker_provider_context.cc b/content/child/service_worker/service_worker_provider_context.cc
index 129d557..d8273aa 100644
--- a/content/child/service_worker/service_worker_provider_context.cc
+++ b/content/child/service_worker/service_worker_provider_context.cc
@@ -7,7 +7,7 @@
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "base/stl_util.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/service_worker/service_worker_dispatcher.h"
 #include "content/child/service_worker/service_worker_handle_reference.h"
 #include "content/child/service_worker/service_worker_registration_handle_reference.h"
@@ -20,9 +20,9 @@ namespace content {
 ServiceWorkerProviderContext::ServiceWorkerProviderContext(int provider_id)
     : provider_id_(provider_id),
       main_thread_loop_proxy_(base::MessageLoopProxy::current()) {
-  if (!ChildThread::current())
+  if (!ChildThreadImpl::current())
     return;  // May be null in some tests.
-  thread_safe_sender_ = ChildThread::current()->thread_safe_sender();
+  thread_safe_sender_ = ChildThreadImpl::current()->thread_safe_sender();
   ServiceWorkerDispatcher* dispatcher =
       ServiceWorkerDispatcher::GetOrCreateThreadSpecificInstance(
           thread_safe_sender_.get());
diff --git a/content/child/service_worker/web_service_worker_provider_impl.cc b/content/child/service_worker/web_service_worker_provider_impl.cc
index 52b6656..5b7d7406 100644
--- a/content/child/service_worker/web_service_worker_provider_impl.cc
+++ b/content/child/service_worker/web_service_worker_provider_impl.cc
@@ -6,7 +6,6 @@
 
 #include "base/atomic_sequence_num.h"
 #include "base/logging.h"
-#include "content/child/child_thread.h"
 #include "content/child/service_worker/service_worker_dispatcher.h"
 #include "content/child/service_worker/service_worker_handle_reference.h"
 #include "content/child/service_worker/service_worker_provider_context.h"
diff --git a/content/child/shared_worker_devtools_agent.cc b/content/child/shared_worker_devtools_agent.cc
index 3a9b350..26a51ed 100644
--- a/content/child/shared_worker_devtools_agent.cc
+++ b/content/child/shared_worker_devtools_agent.cc
@@ -4,7 +4,7 @@
 
 #include "content/child/shared_worker_devtools_agent.h"
 
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/devtools_messages.h"
 #include "ipc/ipc_channel.h"
 #include "third_party/WebKit/public/platform/WebCString.h"
@@ -95,7 +95,7 @@ void SharedWorkerDevToolsAgent::OnDispatchOnInspectorBackend(
 }
 
 bool SharedWorkerDevToolsAgent::Send(IPC::Message* message) {
-  return ChildThread::current()->Send(message);
+  return ChildThreadImpl::current()->Send(message);
 }
 
 }  // namespace content
diff --git a/content/child/thread_safe_sender.cc b/content/child/thread_safe_sender.cc
index d9ecfd1..b8aef12 100644
--- a/content/child/thread_safe_sender.cc
+++ b/content/child/thread_safe_sender.cc
@@ -5,7 +5,7 @@
 #include "content/child/thread_safe_sender.h"
 
 #include "base/message_loop/message_loop_proxy.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "ipc/ipc_sync_message_filter.h"
 
 namespace content {
@@ -21,7 +21,7 @@ ThreadSafeSender::~ThreadSafeSender() {
 
 bool ThreadSafeSender::Send(IPC::Message* msg) {
   if (main_loop_->BelongsToCurrentThread())
-    return ChildThread::current()->Send(msg);
+    return ChildThreadImpl::current()->Send(msg);
   return sync_filter_->Send(msg);
 }
 
diff --git a/content/child/thread_safe_sender.h b/content/child/thread_safe_sender.h
index 443e20a..37ad96b 100644
--- a/content/child/thread_safe_sender.h
+++ b/content/child/thread_safe_sender.h
@@ -19,9 +19,9 @@ class SyncMessageFilter;
 }
 
 namespace content {
-class ChildThread;
+class ChildThreadImpl;
 
-// The class of Sender returned by ChildThread::thread_safe_sender().
+// The class of Sender returned by ChildThreadImpl::thread_safe_sender().
 class CONTENT_EXPORT ThreadSafeSender
     : public IPC::Sender,
       public base::RefCountedThreadSafe<ThreadSafeSender> {
@@ -29,7 +29,7 @@ class CONTENT_EXPORT ThreadSafeSender
   bool Send(IPC::Message* msg) override;
 
  private:
-  friend class ChildThread;  // for construction
+  friend class ChildThreadImpl;  // for construction
   friend class IndexedDBDispatcherTest;
   friend class WebIDBCursorImplTest;
   friend class base::RefCountedThreadSafe<ThreadSafeSender>;
diff --git a/content/child/threaded_data_provider.cc b/content/child/threaded_data_provider.cc
index ccfe891..69ed34b 100644
--- a/content/child/threaded_data_provider.cc
+++ b/content/child/threaded_data_provider.cc
@@ -5,7 +5,7 @@
 #include "content/child/threaded_data_provider.h"
 
 #include "content/child/child_process.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/resource_dispatcher.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/child/webthread_impl.h"
@@ -127,12 +127,12 @@ ThreadedDataProvider::ThreadedDataProvider(
       shm_size_(shm_size),
       background_thread_(static_cast<WebThreadImpl&>(
           *threaded_data_receiver->backgroundThread())),
-      ipc_channel_(ChildThread::current()->channel()),
+      ipc_channel_(ChildThreadImpl::current()->channel()),
       threaded_data_receiver_(threaded_data_receiver),
       resource_filter_active_(false),
       main_thread_task_runner_(main_thread_task_runner),
       main_thread_weak_factory_(this) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   DCHECK(ipc_channel_);
   DCHECK(threaded_data_receiver_);
   DCHECK(main_thread_task_runner_.get());
@@ -146,19 +146,19 @@ ThreadedDataProvider::ThreadedDataProvider(
       background_thread_weak_factory_->GetWeakPtr(),
       main_thread_weak_factory_.GetWeakPtr(), request_id);
 
-  ChildThread::current()->channel()->AddFilter(filter_.get());
+  ChildThreadImpl::current()->channel()->AddFilter(filter_.get());
 }
 
 ThreadedDataProvider::~ThreadedDataProvider() {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
 
-  ChildThread::current()->channel()->RemoveFilter(filter_.get());
+  ChildThreadImpl::current()->channel()->RemoveFilter(filter_.get());
 
   delete threaded_data_receiver_;
 }
 
 void DestructOnMainThread(ThreadedDataProvider* data_provider) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
 
   // The ThreadedDataProvider must be destructed on the main thread to
   // be threadsafe when removing the message filter and releasing the shared
@@ -167,7 +167,7 @@ void DestructOnMainThread(ThreadedDataProvider* data_provider) {
 }
 
 void ThreadedDataProvider::Stop() {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
 
   // Make sure we don't get called by on the main thread anymore via weak
   // pointers we've passed to the filter.
@@ -207,7 +207,7 @@ void ThreadedDataProvider::StopOnBackgroundThread() {
 }
 
 void ThreadedDataProvider::OnResourceMessageFilterAddedMainThread() {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   DCHECK(background_thread_weak_factory_);
 
   // We bounce this message from the I/O thread via the main thread and then
@@ -264,7 +264,7 @@ void ThreadedDataProvider::OnReceivedDataOnBackgroundThread(
 
 void ThreadedDataProvider::OnReceivedDataOnForegroundThread(
     const char* data, int data_length, int encoded_data_length) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
 
   background_thread_.message_loop()->PostTask(FROM_HERE,
       base::Bind(&ThreadedDataProvider::ForwardAndACKData,
diff --git a/content/child/webblobregistry_impl.cc b/content/child/webblobregistry_impl.cc
index 81a1f4b..7b4ec42 100644
--- a/content/child/webblobregistry_impl.cc
+++ b/content/child/webblobregistry_impl.cc
@@ -9,7 +9,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/shared_memory.h"
 #include "base/message_loop/message_loop.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/common/fileapi/webblob_messages.h"
 #include "storage/common/data_element.h"
@@ -158,7 +158,7 @@ void WebBlobRegistryImpl::SendOversizedDataForBlob(
   // writing it directly to the IPC channel.
   size_t shared_memory_size = std::min(data.size(), kMaxSharedMemoryBytes);
   scoped_ptr<base::SharedMemory> shared_memory(
-      ChildThread::AllocateSharedMemory(shared_memory_size, sender_.get()));
+      ChildThreadImpl::AllocateSharedMemory(shared_memory_size, sender_.get()));
   CHECK(shared_memory.get());
   if (!shared_memory->Map(shared_memory_size))
     CHECK(false);
@@ -179,19 +179,19 @@ void WebBlobRegistryImpl::SendOversizedDataForBlob(
 
 void WebBlobRegistryImpl::registerStreamURL(
     const WebURL& url, const WebString& content_type) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_StartBuilding(url, content_type.utf8()));
 }
 
 void WebBlobRegistryImpl::registerStreamURL(
     const WebURL& url, const WebURL& src_url) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_Clone(url, src_url));
 }
 
 void WebBlobRegistryImpl::addDataToStream(const WebURL& url,
                                           const char* data, size_t length) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   if (length == 0)
     return;
   if (length < kLargeThresholdBytes) {
@@ -204,8 +204,8 @@ void WebBlobRegistryImpl::addDataToStream(const WebURL& url,
     size_t shared_memory_size = std::min(
         length, kMaxSharedMemoryBytes);
     scoped_ptr<base::SharedMemory> shared_memory(
-        ChildThread::AllocateSharedMemory(shared_memory_size,
-                                          sender_.get()));
+        ChildThreadImpl::AllocateSharedMemory(shared_memory_size,
+                                              sender_.get()));
     CHECK(shared_memory.get());
     if (!shared_memory->Map(shared_memory_size))
       CHECK(false);
@@ -224,22 +224,22 @@ void WebBlobRegistryImpl::addDataToStream(const WebURL& url,
 }
 
 void WebBlobRegistryImpl::flushStream(const WebURL& url) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_Flush(url));
 }
 
 void WebBlobRegistryImpl::finalizeStream(const WebURL& url) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_FinishBuilding(url));
 }
 
 void WebBlobRegistryImpl::abortStream(const WebURL& url) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_AbortBuilding(url));
 }
 
 void WebBlobRegistryImpl::unregisterStreamURL(const WebURL& url) {
-  DCHECK(ChildThread::current());
+  DCHECK(ChildThreadImpl::current());
   sender_->Send(new StreamHostMsg_Remove(url));
 }
 
diff --git a/content/child/webmessageportchannel_impl.cc b/content/child/webmessageportchannel_impl.cc
index c3de36f..725e595 100644
--- a/content/child/webmessageportchannel_impl.cc
+++ b/content/child/webmessageportchannel_impl.cc
@@ -7,7 +7,7 @@
 #include "base/bind.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "content/child/child_process.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/message_port_messages.h"
 #include "third_party/WebKit/public/platform/WebMessagePortChannelClient.h"
 #include "third_party/WebKit/public/platform/WebString.h"
@@ -56,7 +56,7 @@ WebMessagePortChannelImpl::~WebMessagePortChannelImpl() {
     Send(new MessagePortHostMsg_DestroyMessagePort(message_port_id_));
 
   if (route_id_ != MSG_ROUTING_NONE)
-    ChildThread::current()->GetRouter()->RemoveRoute(route_id_);
+    ChildThreadImpl::current()->GetRouter()->RemoveRoute(route_id_);
 }
 
 // static
@@ -169,7 +169,7 @@ void WebMessagePortChannelImpl::Init() {
     Send(new MessagePortHostMsg_ReleaseMessages(message_port_id_));
   }
 
-  ChildThread::current()->GetRouter()->AddRoute(route_id_, this);
+  ChildThreadImpl::current()->GetRouter()->AddRoute(route_id_, this);
 }
 
 void WebMessagePortChannelImpl::Entangle(
@@ -216,7 +216,7 @@ void WebMessagePortChannelImpl::Send(IPC::Message* message) {
     return;
   }
 
-  ChildThread::current()->GetRouter()->Send(message);
+  ChildThreadImpl::current()->GetRouter()->Send(message);
 }
 
 bool WebMessagePortChannelImpl::OnMessageReceived(const IPC::Message& message) {
diff --git a/content/child/websocket_bridge.cc b/content/child/websocket_bridge.cc
index 5b32702..e091023 100644
--- a/content/child/websocket_bridge.cc
+++ b/content/child/websocket_bridge.cc
@@ -11,7 +11,7 @@
 
 #include "base/logging.h"
 #include "base/strings/string_util.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/websocket_dispatcher.h"
 #include "content/common/websocket.h"
 #include "content/common/websocket_messages.h"
@@ -52,7 +52,7 @@ WebSocketBridge::~WebSocketBridge() {
   if (channel_id_ != kInvalidChannelId) {
     // The connection is abruptly disconnected by the renderer without
     // closing handshake.
-    ChildThread::current()->Send(
+    ChildThreadImpl::current()->Send(
         new WebSocketMsg_DropChannel(channel_id_,
                                      false,
                                      kAbnormalShutdownOpCode,
@@ -214,7 +214,7 @@ void WebSocketBridge::connect(
     WebSocketHandleClient* client) {
   DCHECK_EQ(kInvalidChannelId, channel_id_);
   WebSocketDispatcher* dispatcher =
-      ChildThread::current()->websocket_dispatcher();
+      ChildThreadImpl::current()->websocket_dispatcher();
   channel_id_ = dispatcher->AddBridge(this);
   client_ = client;
 
@@ -227,7 +227,7 @@ void WebSocketBridge::connect(
            << JoinString(protocols_to_pass, ", ") << "), "
            << origin_to_pass.string() << ")";
 
-  ChildThread::current()->Send(new WebSocketHostMsg_AddChannelRequest(
+  ChildThreadImpl::current()->Send(new WebSocketHostMsg_AddChannelRequest(
       channel_id_, url, protocols_to_pass, origin_to_pass, render_frame_id_));
 }
 
@@ -255,7 +255,7 @@ void WebSocketBridge::send(bool fin,
            << fin << ", " << type_to_pass << ", "
            << "(data size = "  << size << "))";
 
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new WebSocketMsg_SendFrame(channel_id_,
                                  fin,
                                  type_to_pass,
@@ -268,7 +268,7 @@ void WebSocketBridge::flowControl(int64_t quota) {
 
   DVLOG(1) << "Bridge #" << channel_id_ << " FlowControl(" << quota << ")";
 
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new WebSocketMsg_FlowControl(channel_id_, quota));
 }
 
@@ -281,7 +281,7 @@ void WebSocketBridge::close(unsigned short code,
   DVLOG(1) << "Bridge #" << channel_id_ << " Close("
            << code << ", " << reason_to_pass << ")";
   // This method is for closing handshake and hence |was_clean| shall be true.
-  ChildThread::current()->Send(
+  ChildThreadImpl::current()->Send(
       new WebSocketMsg_DropChannel(channel_id_, true, code, reason_to_pass));
 }
 
@@ -289,7 +289,7 @@ void WebSocketBridge::Disconnect() {
   if (channel_id_ == kInvalidChannelId)
     return;
   WebSocketDispatcher* dispatcher =
-      ChildThread::current()->websocket_dispatcher();
+      ChildThreadImpl::current()->websocket_dispatcher();
   dispatcher->RemoveBridge(channel_id_);
 
   channel_id_ = kInvalidChannelId;
diff --git a/content/content_child.gypi b/content/content_child.gypi
index 013d2e5..bfde2e2 100644
--- a/content/content_child.gypi
+++ b/content/content_child.gypi
@@ -23,6 +23,7 @@
   ],
   'variables': {
     'public_child_sources': [
+      'public/child/child_thread.h',
       'public/child/image_decoder_utils.h',
       'public/child/request_peer.h',
       'public/child/resource_dispatcher_delegate.h',
@@ -61,8 +62,8 @@
       'child/child_resource_message_filter.h',
       'child/child_shared_bitmap_manager.cc',
       'child/child_shared_bitmap_manager.h',
-      'child/child_thread.cc',
-      'child/child_thread.h',
+      'child/child_thread_impl.cc',
+      'child/child_thread_impl.h',
       'child/content_child_helpers.cc',
       'child/content_child_helpers.h',
       'child/database_util.cc',
diff --git a/content/gpu/gpu_child_thread.cc b/content/gpu/gpu_child_thread.cc
index b7846f4..1064a70 100644
--- a/content/gpu/gpu_child_thread.cc
+++ b/content/gpu/gpu_child_thread.cc
@@ -44,8 +44,8 @@ bool GpuProcessLogMessageHandler(int severity,
   return false;
 }
 
-ChildThread::Options GetOptions() {
-  ChildThread::Options options;
+ChildThreadImpl::Options GetOptions() {
+  ChildThreadImpl::Options options;
 
 #if defined(USE_OZONE)
   IPC::MessageFilter* message_filter = ui::OzonePlatform::GetInstance()
@@ -64,7 +64,7 @@ GpuChildThread::GpuChildThread(GpuWatchdogThread* watchdog_thread,
                                bool dead_on_arrival,
                                const gpu::GPUInfo& gpu_info,
                                const DeferredMessages& deferred_messages)
-    : ChildThread(GetOptions()),
+    : ChildThreadImpl(GetOptions()),
       dead_on_arrival_(dead_on_arrival),
       gpu_info_(gpu_info),
       deferred_messages_(deferred_messages),
@@ -77,7 +77,7 @@ GpuChildThread::GpuChildThread(GpuWatchdogThread* watchdog_thread,
 }
 
 GpuChildThread::GpuChildThread(const std::string& channel_id)
-    : ChildThread(Options(channel_id, false)),
+    : ChildThreadImpl(Options(channel_id, false)),
       dead_on_arrival_(false),
       in_browser_process_(true) {
 #if defined(OS_WIN)
@@ -102,7 +102,7 @@ GpuChildThread::~GpuChildThread() {
 }
 
 void GpuChildThread::Shutdown() {
-  ChildThread::Shutdown();
+  ChildThreadImpl::Shutdown();
   logging::SetLogMessageHandler(NULL);
 }
 
@@ -115,7 +115,7 @@ bool GpuChildThread::Send(IPC::Message* msg) {
   // process. This could result in deadlock.
   DCHECK(!msg->is_sync());
 
-  return ChildThread::Send(msg);
+  return ChildThreadImpl::Send(msg);
 }
 
 bool GpuChildThread::OnControlMessageReceived(const IPC::Message& msg) {
diff --git a/content/gpu/gpu_child_thread.h b/content/gpu/gpu_child_thread.h
index b5c312d..7103cd3 100644
--- a/content/gpu/gpu_child_thread.h
+++ b/content/gpu/gpu_child_thread.h
@@ -14,7 +14,7 @@
 #include "base/memory/scoped_ptr.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/gpu/gpu_channel.h"
 #include "content/common/gpu/gpu_channel_manager.h"
 #include "content/common/gpu/gpu_config.h"
@@ -33,7 +33,7 @@ class GpuWatchdogThread;
 // these per process. It does process initialization and shutdown. It forwards
 // IPC messages to GpuChannelManager, which is responsible for issuing rendering
 // commands to the GPU.
-class GpuChildThread : public ChildThread {
+class GpuChildThread : public ChildThreadImpl {
  public:
   typedef std::queue<IPC::Message*> DeferredMessages;
 
diff --git a/content/plugin/plugin_thread.cc b/content/plugin/plugin_thread.cc
index 720a77b..a688902 100644
--- a/content/plugin/plugin_thread.cc
+++ b/content/plugin/plugin_thread.cc
@@ -106,7 +106,7 @@ void PluginThread::SetForcefullyTerminatePluginProcess() {
 }
 
 void PluginThread::Shutdown() {
-  ChildThread::Shutdown();
+  ChildThreadImpl::Shutdown();
 
   if (preloaded_plugin_module_) {
     base::UnloadNativeLibrary(preloaded_plugin_module_);
diff --git a/content/plugin/plugin_thread.h b/content/plugin/plugin_thread.h
index 11acafc..8ad115e 100644
--- a/content/plugin/plugin_thread.h
+++ b/content/plugin/plugin_thread.h
@@ -8,7 +8,7 @@
 #include "base/files/file_path.h"
 #include "base/native_library.h"
 #include "build/build_config.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/npapi/plugin_lib.h"
 #include "content/plugin/plugin_channel.h"
 
@@ -22,7 +22,7 @@ class BlinkPlatformImpl;
 // The PluginThread class represents a background thread where plugin instances
 // live.  Communication occurs between WebPluginDelegateProxy in the renderer
 // process and WebPluginDelegateStub in this thread through IPC messages.
-class PluginThread : public ChildThread {
+class PluginThread : public ChildThreadImpl {
  public:
   PluginThread();
   ~PluginThread() override;
diff --git a/content/ppapi_plugin/ppapi_blink_platform_impl.cc b/content/ppapi_plugin/ppapi_blink_platform_impl.cc
index ad84196..793f6d6 100644
--- a/content/ppapi_plugin/ppapi_blink_platform_impl.cc
+++ b/content/ppapi_plugin/ppapi_blink_platform_impl.cc
@@ -10,7 +10,7 @@
 #include "base/strings/string16.h"
 #include "base/threading/platform_thread.h"
 #include "build/build_config.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/child_process_messages.h"
 #include "ppapi/proxy/plugin_globals.h"
 #include "ppapi/shared_impl/proxy_lock.h"
diff --git a/content/ppapi_plugin/ppapi_thread.cc b/content/ppapi_plugin/ppapi_thread.cc
index 6d77afe..103a7b8 100644
--- a/content/ppapi_plugin/ppapi_thread.cc
+++ b/content/ppapi_plugin/ppapi_thread.cc
@@ -42,12 +42,10 @@
 #include "ppapi/proxy/plugin_message_filter.h"
 #include "ppapi/proxy/ppapi_messages.h"
 #include "ppapi/proxy/resource_reply_thread_registrar.h"
-#include "ppapi/shared_impl/proxy_lock.h"
 #include "third_party/WebKit/public/web/WebKit.h"
 #include "ui/base/ui_base_switches.h"
 
 #if defined(OS_WIN)
-#include "base/win/iat_patch_function.h"
 #include "base/win/win_util.h"
 #include "base/win/windows_version.h"
 #include "sandbox/win/src/sandbox.h"
@@ -94,54 +92,6 @@ static void WarmupWindowsLocales(const ppapi::PpapiPermissions& permissions) {
   }
 }
 
-// TODO(scottmg): http://crbug.com/448473. This code should be removed from the
-// renderer once PDF is always OOP and/or PDF is made to use Skia instead of GDI
-// directly.
-const wchar_t kPdfFileName[] = L"pdf.dll";
-
-static base::win::IATPatchFunction g_iat_patch_createdca;
-HDC WINAPI CreateDCAPatch(LPCSTR driver_name,
-                          LPCSTR device_name,
-                          LPCSTR output,
-                          const void* init_data) {
-  DCHECK(std::string("DISPLAY") == std::string(driver_name));
-  DCHECK(!device_name);
-  DCHECK(!output);
-  DCHECK(!init_data);
-
-  // CreateDC fails behind the sandbox, but not CreateCompatibleDC.
-  return CreateCompatibleDC(NULL);
-}
-
-static base::win::IATPatchFunction g_iat_patch_get_font_data;
-DWORD WINAPI GetFontDataPatch(HDC hdc,
-                              DWORD table,
-                              DWORD offset,
-                              LPVOID buffer,
-                              DWORD length) {
-  int rv = GetFontData(hdc, table, offset, buffer, length);
-  if (rv == GDI_ERROR && hdc) {
-    HFONT font = static_cast<HFONT>(GetCurrentObject(hdc, OBJ_FONT));
-
-    LOGFONT logfont;
-    if (GetObject(font, sizeof(LOGFONT), &logfont)) {
-      std::vector<char> font_data;
-      {
-        ppapi::ProxyAutoLock lock;
-        // In the sandbox, font loading will fail. We ask the browser to load it
-        // which causes it to be loaded by the kernel, which then makes the
-        // subsequent call succeed.
-        ppapi::proxy::PluginGlobals::Get()->PreCacheFontForFlash(
-            reinterpret_cast<const void*>(&logfont));
-      }
-      rv = GetFontData(hdc, table, offset, buffer, length);
-    }
-  }
-  return rv;
-}
-
-#else
-extern void* g_target_services;
 #endif
 
 namespace content {
@@ -173,7 +123,7 @@ PpapiThread::~PpapiThread() {
 }
 
 void PpapiThread::Shutdown() {
-  ChildThread::Shutdown();
+  ChildThreadImpl::Shutdown();
 
   ppapi::proxy::PluginGlobals::Get()->ResetPluginProxyDelegate();
   if (plugin_entry_points_.shutdown_module)
@@ -185,7 +135,7 @@ void PpapiThread::Shutdown() {
 bool PpapiThread::Send(IPC::Message* msg) {
   // Allow access from multiple threads.
   if (base::MessageLoop::current() == message_loop())
-    return ChildThread::Send(msg);
+    return ChildThreadImpl::Send(msg);
 
   return sync_message_filter()->Send(msg);
 }
@@ -207,7 +157,7 @@ bool PpapiThread::OnControlMessageReceived(const IPC::Message& msg) {
 }
 
 void PpapiThread::OnChannelConnected(int32 peer_pid) {
-  ChildThread::OnChannelConnected(peer_pid);
+  ChildThreadImpl::OnChannelConnected(peer_pid);
 #if defined(OS_WIN)
   if (is_broker_)
     peer_handle_.Set(::OpenProcess(PROCESS_DUP_HANDLE, FALSE, peer_pid));
@@ -253,8 +203,7 @@ std::string PpapiThread::GetUILanguage() {
 
 void PpapiThread::PreCacheFont(const void* logfontw) {
 #if defined(OS_WIN)
-  Send(new ChildProcessHostMsg_PreCacheFont(
-      *static_cast<const LOGFONTW*>(logfontw)));
+  ChildThreadImpl::PreCacheFont(*static_cast<const LOGFONTW*>(logfontw));
 #endif
 }
 
@@ -374,15 +323,6 @@ void PpapiThread::OnLoadPlugin(const base::FilePath& path,
   // otherwise these would be silent terminations and fly under the radar).
   base::win::SetAbortBehaviorForCrashReporting();
 
-  // Need to patch a few functions for font loading to work correctly. This can
-  // be removed once we switch PDF to use Skia.
-  if (GetModuleHandle(kPdfFileName)) {
-    g_iat_patch_createdca.Patch(kPdfFileName, "gdi32.dll", "CreateDCA",
-                                CreateDCAPatch);
-    g_iat_patch_get_font_data.Patch(kPdfFileName, "gdi32.dll", "GetFontData",
-                                    GetFontDataPatch);
-  }
-
   // Once we lower the token the sandbox is locked down and no new modules
   // can be loaded. TODO(cpu): consider changing to the loading style of
   // regular plugins.
diff --git a/content/ppapi_plugin/ppapi_thread.h b/content/ppapi_plugin/ppapi_thread.h
index 3d80e49..8b4f522 100644
--- a/content/ppapi_plugin/ppapi_thread.h
+++ b/content/ppapi_plugin/ppapi_thread.h
@@ -14,7 +14,7 @@
 #include "base/process/process.h"
 #include "base/scoped_native_library.h"
 #include "build/build_config.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/public/common/pepper_plugin_info.h"
 #include "ppapi/c/pp_module.h"
 #include "ppapi/c/trusted/ppp_broker.h"
@@ -40,7 +40,13 @@ namespace content {
 
 class PpapiBlinkPlatformImpl;
 
-class PpapiThread : public ChildThread,
+#if defined(COMPILER_MSVC)
+// See explanation for other RenderViewHostImpl which is the same issue.
+#pragma warning(push)
+#pragma warning(disable: 4250)
+#endif
+
+class PpapiThread : public ChildThreadImpl,
                     public ppapi::proxy::PluginDispatcher::PluginDelegate,
                     public ppapi::proxy::PluginProxyDelegate {
  public:
@@ -158,6 +164,10 @@ class PpapiThread : public ChildThread,
   DISALLOW_IMPLICIT_CONSTRUCTORS(PpapiThread);
 };
 
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)
+#endif
+
 }  // namespace content
 
 #endif  // CONTENT_PPAPI_PLUGIN_PPAPI_THREAD_H_
diff --git a/content/public/child/child_thread.h b/content/public/child/child_thread.h
new file mode 100644
index 0000000..e3df72c
--- /dev/null
+++ b/content/public/child/child_thread.h
@@ -0,0 +1,37 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef CONTENT_PUBLIC_CHILD_THREAD_H_
+#define CONTENT_PUBLIC_CHILD_THREAD_H_
+
+#include "content/common/content_export.h"
+#include "ipc/ipc_sender.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#endif
+
+namespace content {
+
+class CONTENT_EXPORT ChildThread : public IPC::Sender {
+ public:
+  // Returns the one child thread for this process.  Note that this can only be
+  // accessed when running on the child thread itself.
+  static ChildThread* Get();
+
+  ~ChildThread() override {}
+
+#if defined(OS_WIN)
+  // Request that the given font be loaded by the browser so it's cached by the
+  // OS. Please see ChildProcessHost::PreCacheFont for details.
+  virtual void PreCacheFont(const LOGFONT& log_font) = 0;
+
+  // Release cached font.
+  virtual void ReleaseCachedFonts() = 0;
+#endif
+};
+
+}  // namespace content
+
+#endif  // CONTENT_PUBLIC_CHILD_THREAD_H_
diff --git a/content/public/renderer/DEPS b/content/public/renderer/DEPS
index 36c27b9..f78d4a3 100644
--- a/content/public/renderer/DEPS
+++ b/content/public/renderer/DEPS
@@ -1,4 +1,5 @@
 include_rules = [
+  "+content/public/child",
   "+media/base",
   "+media/filters",
   "+media/video",
diff --git a/content/public/renderer/render_thread.h b/content/public/renderer/render_thread.h
index 002f45d..407128b 100644
--- a/content/public/renderer/render_thread.h
+++ b/content/public/renderer/render_thread.h
@@ -10,12 +10,8 @@
 #include "base/memory/shared_memory.h"
 #include "base/metrics/user_metrics_action.h"
 #include "content/common/content_export.h"
+#include "content/public/child/child_thread.h"
 #include "ipc/ipc_channel_proxy.h"
-#include "ipc/ipc_sender.h"
-
-#if defined(OS_WIN)
-#include <windows.h>
-#endif
 
 class GURL;
 
@@ -45,7 +41,7 @@ class RenderProcessObserver;
 class ResourceDispatcherDelegate;
 class ServiceRegistry;
 
-class CONTENT_EXPORT RenderThread : public IPC::Sender {
+class CONTENT_EXPORT RenderThread : virtual public ChildThread {
  public:
   // Returns the one render thread for this process.  Note that this can only
   // be accessed when running on the render thread itself.
@@ -135,15 +131,6 @@ class CONTENT_EXPORT RenderThread : public IPC::Sender {
   // Gets the shutdown event for the process.
   virtual base::WaitableEvent* GetShutdownEvent() = 0;
 
-#if defined(OS_WIN)
-  // Request that the given font be loaded by the browser so it's cached by the
-  // OS. Please see ChildProcessHost::PreCacheFont for details.
-  virtual void PreCacheFont(const LOGFONT& log_font) = 0;
-
-  // Release cached font.
-  virtual void ReleaseCachedFonts() = 0;
-#endif
-
   // Returns the ServiceRegistry for this thread.
   virtual ServiceRegistry* GetServiceRegistry() = 0;
 };
diff --git a/content/public/utility/DEPS b/content/public/utility/DEPS
new file mode 100644
index 0000000..ad94e88
--- /dev/null
+++ b/content/public/utility/DEPS
@@ -0,0 +1,3 @@
+include_rules = [
+  "+content/public/child",
+]
diff --git a/content/public/utility/utility_thread.h b/content/public/utility/utility_thread.h
index 6e7cbd1..42bf10c 100644
--- a/content/public/utility/utility_thread.h
+++ b/content/public/utility/utility_thread.h
@@ -6,16 +6,11 @@
 #define CONTENT_PUBLIC_UTILITY_UTILITY_THREAD_H_
 
 #include "base/basictypes.h"
-#include "content/common/content_export.h"
-#include "ipc/ipc_sender.h"
-
-#if defined(OS_WIN)
-#include <windows.h>
-#endif
+#include "content/public/child/child_thread.h"
 
 namespace content {
 
-class CONTENT_EXPORT UtilityThread : public IPC::Sender {
+class CONTENT_EXPORT UtilityThread : virtual public ChildThread {
  public:
   // Returns the one utility thread for this process.  Note that this can only
   // be accessed when running on the utility thread itself.
@@ -26,15 +21,6 @@ class CONTENT_EXPORT UtilityThread : public IPC::Sender {
 
   // Releases the process if we are not (or no longer) in batch mode.
   virtual void ReleaseProcessIfNeeded() = 0;
-
-#if defined(OS_WIN)
-  // Request that the given font be loaded by the browser so it's cached by the
-  // OS. Please see ChildProcessHost::PreCacheFont for details.
-  virtual void PreCacheFont(const LOGFONT& log_font) = 0;
-
-  // Release cached font.
-  virtual void ReleaseCachedFonts() = 0;
-#endif
 };
 
 }  // namespace content
diff --git a/content/renderer/geolocation_dispatcher.cc b/content/renderer/geolocation_dispatcher.cc
index ce56f8e..65b85a1 100644
--- a/content/renderer/geolocation_dispatcher.cc
+++ b/content/renderer/geolocation_dispatcher.cc
@@ -4,7 +4,6 @@
 
 #include "content/renderer/geolocation_dispatcher.h"
 
-#include "content/child/child_thread.h"
 #include "content/public/common/geoposition.h"
 #include "content/renderer/render_view_impl.h"
 #include "third_party/WebKit/public/platform/WebString.h"
diff --git a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
index 9c24682..66f3d28 100644
--- a/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
+++ b/content/renderer/media/renderer_gpu_video_accelerator_factories.cc
@@ -8,7 +8,7 @@
 #include <GLES2/gl2ext.h>
 
 #include "base/bind.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/gpu/client/context_provider_command_buffer.h"
 #include "content/common/gpu/client/gl_helper.h"
 #include "content/common/gpu/client/gpu_channel_host.h"
@@ -48,7 +48,7 @@ RendererGpuVideoAcceleratorFactories::RendererGpuVideoAcceleratorFactories(
     : task_runner_(task_runner),
       gpu_channel_host_(gpu_channel_host),
       context_provider_(context_provider),
-      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {}
+      thread_safe_sender_(ChildThreadImpl::current()->thread_safe_sender()) {}
 
 RendererGpuVideoAcceleratorFactories::~RendererGpuVideoAcceleratorFactories() {}
 
@@ -239,7 +239,7 @@ scoped_ptr<base::SharedMemory>
 RendererGpuVideoAcceleratorFactories::CreateSharedMemory(size_t size) {
   DCHECK(task_runner_->BelongsToCurrentThread());
   scoped_ptr<base::SharedMemory> mem(
-      ChildThread::AllocateSharedMemory(size, thread_safe_sender_.get()));
+      ChildThreadImpl::AllocateSharedMemory(size, thread_safe_sender_.get()));
   if (mem && !mem->Map(size))
     return nullptr;
   return mem;
diff --git a/content/renderer/media/rtc_video_decoder.cc b/content/renderer/media/rtc_video_decoder.cc
index ffa2536..0bfc9d8 100644
--- a/content/renderer/media/rtc_video_decoder.cc
+++ b/content/renderer/media/rtc_video_decoder.cc
@@ -13,7 +13,6 @@
 #include "base/stl_util.h"
 #include "base/synchronization/waitable_event.h"
 #include "base/task_runner_util.h"
-#include "content/child/child_thread.h"
 #include "content/renderer/media/native_handle_impl.h"
 #include "gpu/command_buffer/common/mailbox_holder.h"
 #include "media/base/bind_to_current_loop.h"
diff --git a/content/renderer/npapi/webplugin_delegate_proxy.cc b/content/renderer/npapi/webplugin_delegate_proxy.cc
index 32cac5d..66bc362 100644
--- a/content/renderer/npapi/webplugin_delegate_proxy.cc
+++ b/content/renderer/npapi/webplugin_delegate_proxy.cc
@@ -640,7 +640,7 @@ bool WebPluginDelegateProxy::CreateLocalBitmap(
 bool WebPluginDelegateProxy::CreateSharedBitmap(
     scoped_ptr<SharedMemoryBitmap>* memory,
     scoped_ptr<skia::PlatformCanvas>* canvas) {
-  *memory = ChildThread::current()
+  *memory = ChildThreadImpl::current()
                 ->shared_bitmap_manager()
                 ->AllocateSharedMemoryBitmap(plugin_rect_.size());
   if (!memory->get())
diff --git a/content/renderer/pepper/pepper_compositor_host.cc b/content/renderer/pepper/pepper_compositor_host.cc
index c5f5e98..eec292a 100644
--- a/content/renderer/pepper/pepper_compositor_host.cc
+++ b/content/renderer/pepper/pepper_compositor_host.cc
@@ -12,7 +12,7 @@
 #include "cc/resources/texture_mailbox.h"
 #include "cc/trees/layer_tree_host.h"
 #include "content/child/child_shared_bitmap_manager.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/public/renderer/renderer_ppapi_host.h"
 #include "content/renderer/pepper/gfx_conversion.h"
 #include "content/renderer/pepper/host_globals.h"
@@ -288,7 +288,7 @@ void PepperCompositorHost::UpdateLayer(
       DCHECK_EQ(desc.stride, desc.size.width * 4);
       DCHECK_EQ(desc.format, PP_IMAGEDATAFORMAT_RGBA_PREMUL);
       scoped_ptr<cc::SharedBitmap> bitmap =
-          ChildThread::current()
+          ChildThreadImpl::current()
               ->shared_bitmap_manager()
               ->GetBitmapForSharedMemory(image_shm.get());
 
diff --git a/content/renderer/pepper/pepper_file_system_host.cc b/content/renderer/pepper/pepper_file_system_host.cc
index 6994534..bce63a2 100644
--- a/content/renderer/pepper/pepper_file_system_host.cc
+++ b/content/renderer/pepper/pepper_file_system_host.cc
@@ -6,7 +6,7 @@
 
 #include "base/bind.h"
 #include "base/callback.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/fileapi/file_system_dispatcher.h"
 #include "content/common/pepper_file_util.h"
 #include "content/renderer/pepper/pepper_plugin_instance_impl.h"
@@ -102,7 +102,7 @@ int32_t PepperFileSystemHost::OnHostMsgOpen(
     return PP_ERROR_FAILED;
 
   FileSystemDispatcher* file_system_dispatcher =
-      ChildThread::current()->file_system_dispatcher();
+      ChildThreadImpl::current()->file_system_dispatcher();
   reply_context_ = context->MakeReplyMessageContext();
   file_system_dispatcher->OpenFileSystem(
       document_url.GetOrigin(),
diff --git a/content/renderer/pepper/ppb_broker_impl.cc b/content/renderer/pepper/ppb_broker_impl.cc
index 33181a25..ead54a0 100644
--- a/content/renderer/pepper/ppb_broker_impl.cc
+++ b/content/renderer/pepper/ppb_broker_impl.cc
@@ -32,7 +32,7 @@ PPB_Broker_Impl::PPB_Broker_Impl(PP_Instance instance)
       connect_callback_(),
       pipe_handle_(PlatformFileToInt(base::SyncSocket::kInvalidHandle)),
       routing_id_(RenderThreadImpl::current()->GenerateRoutingID()) {
-  ChildThread::current()->GetRouter()->AddRoute(routing_id_, this);
+  ChildThreadImpl::current()->GetRouter()->AddRoute(routing_id_, this);
 }
 
 PPB_Broker_Impl::~PPB_Broker_Impl() {
@@ -43,7 +43,7 @@ PPB_Broker_Impl::~PPB_Broker_Impl() {
 
   // The plugin owns the handle.
   pipe_handle_ = PlatformFileToInt(base::SyncSocket::kInvalidHandle);
-  ChildThread::current()->GetRouter()->RemoveRoute(routing_id_);
+  ChildThreadImpl::current()->GetRouter()->RemoveRoute(routing_id_);
 }
 
 PPB_Broker_API* PPB_Broker_Impl::AsPPB_Broker_API() { return this; }
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 876e8ae..9ad8d4f 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -2041,13 +2041,13 @@ blink::WebServiceWorkerProvider* RenderFrameImpl::createServiceWorkerProvider(
   DCHECK(!frame_ || frame_ == frame);
   // At this point we should have non-null data source.
   DCHECK(frame->dataSource());
-  if (!ChildThread::current())
+  if (!ChildThreadImpl::current())
     return NULL;  // May be null in some tests.
   ServiceWorkerNetworkProvider* provider =
       ServiceWorkerNetworkProvider::FromDocumentState(
           DocumentState::FromDataSource(frame->dataSource()));
   return new WebServiceWorkerProviderImpl(
-      ChildThread::current()->thread_safe_sender(),
+      ChildThreadImpl::current()->thread_safe_sender(),
       provider ? provider->context() : NULL);
 }
 
@@ -3362,7 +3362,7 @@ void RenderFrameImpl::requestStorageQuota(
     callbacks.didFail(blink::WebStorageQuotaErrorAbort);
     return;
   }
-  ChildThread::current()->quota_dispatcher()->RequestStorageQuota(
+  ChildThreadImpl::current()->quota_dispatcher()->RequestStorageQuota(
       render_view_->GetRoutingID(),
       GURL(origin.toString()),
       static_cast<storage::StorageType>(type),
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 2914c9c..533f950 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -282,8 +282,8 @@ void AddHistogramSample(void* hist, int sample) {
 
 scoped_ptr<cc::SharedBitmap> AllocateSharedBitmapFunction(
     const gfx::Size& size) {
-  return ChildThread::current()->shared_bitmap_manager()->AllocateSharedBitmap(
-      size);
+  return ChildThreadImpl::current()->shared_bitmap_manager()->
+      AllocateSharedBitmap(size);
 }
 
 void EnableBlinkPlatformLogChannels(const std::string& channels) {
@@ -423,18 +423,18 @@ RenderThreadImpl* RenderThreadImpl::current() {
 // When we run plugins in process, we actually run them on the render thread,
 // which means that we need to make the render thread pump UI events.
 RenderThreadImpl::RenderThreadImpl()
-    : ChildThread(Options(ShouldUseMojoChannel())) {
+    : ChildThreadImpl(Options(ShouldUseMojoChannel())) {
   Init();
 }
 
 RenderThreadImpl::RenderThreadImpl(const std::string& channel_name)
-    : ChildThread(Options(channel_name, ShouldUseMojoChannel())) {
+    : ChildThreadImpl(Options(channel_name, ShouldUseMojoChannel())) {
   Init();
 }
 
 RenderThreadImpl::RenderThreadImpl(
     scoped_ptr<base::MessageLoop> main_message_loop)
-    : ChildThread(Options(ShouldUseMojoChannel())),
+    : ChildThreadImpl(Options(ShouldUseMojoChannel())),
       main_message_loop_(main_message_loop.Pass()) {
   Init();
 }
@@ -655,7 +655,7 @@ void RenderThreadImpl::Init() {
   }
 
   base::DiscardableMemoryShmemAllocator::SetInstance(
-      ChildThread::discardable_shared_memory_manager());
+      ChildThreadImpl::discardable_shared_memory_manager());
 
   service_registry()->AddService<RenderFrameSetup>(
       base::Bind(CreateRenderFrameSetup));
@@ -670,7 +670,7 @@ void RenderThreadImpl::Shutdown() {
   FOR_EACH_OBSERVER(
       RenderProcessObserver, observers_, OnRenderProcessShutdown());
 
-  ChildThread::Shutdown();
+  ChildThreadImpl::Shutdown();
 
   if (memory_observer_) {
     message_loop()->RemoveTaskObserver(memory_observer_.get());
@@ -811,7 +811,7 @@ bool RenderThreadImpl::Send(IPC::Message* msg) {
 #endif
   }
 
-  bool rv = ChildThread::Send(msg);
+  bool rv = ChildThreadImpl::Send(msg);
 
   if (pumping_events) {
 #if defined(ENABLE_PLUGINS)
@@ -860,7 +860,7 @@ scoped_refptr<base::MessageLoopProxy>
 }
 
 void RenderThreadImpl::AddRoute(int32 routing_id, IPC::Listener* listener) {
-  ChildThread::GetRouter()->AddRoute(routing_id, listener);
+  ChildThreadImpl::GetRouter()->AddRoute(routing_id, listener);
   PendingRenderFrameConnectMap::iterator it =
       pending_render_frame_connects_.find(routing_id);
   if (it == pending_render_frame_connects_.end())
@@ -881,7 +881,7 @@ void RenderThreadImpl::AddRoute(int32 routing_id, IPC::Listener* listener) {
 }
 
 void RenderThreadImpl::RemoveRoute(int32 routing_id) {
-  ChildThread::GetRouter()->RemoveRoute(routing_id);
+  ChildThreadImpl::GetRouter()->RemoveRoute(routing_id);
 }
 
 void RenderThreadImpl::AddEmbeddedWorkerRoute(int32 routing_id,
@@ -1112,7 +1112,7 @@ void RenderThreadImpl::RecordComputedAction(const std::string& action) {
 
 scoped_ptr<base::SharedMemory>
     RenderThreadImpl::HostAllocateSharedMemoryBuffer(size_t size) {
-  return ChildThread::AllocateSharedMemory(size, thread_safe_sender());
+  return ChildThreadImpl::AllocateSharedMemory(size, thread_safe_sender());
 }
 
 cc::SharedBitmapManager* RenderThreadImpl::GetSharedBitmapManager() {
@@ -1326,14 +1326,6 @@ void RenderThreadImpl::PreCacheFontCharacters(const LOGFONT& log_font,
   Send(new ViewHostMsg_PreCacheFontCharacters(log_font, str));
 }
 
-void RenderThreadImpl::PreCacheFont(const LOGFONT& log_font) {
-  Send(new ChildProcessHostMsg_PreCacheFont(log_font));
-}
-
-void RenderThreadImpl::ReleaseCachedFonts() {
-  Send(new ChildProcessHostMsg_ReleaseCachedFonts());
-}
-
 #endif  // OS_WIN
 
 ServiceRegistry* RenderThreadImpl::GetServiceRegistry() {
diff --git a/content/renderer/render_thread_impl.h b/content/renderer/render_thread_impl.h
index e204c63..18ceb7b 100644
--- a/content/renderer/render_thread_impl.h
+++ b/content/renderer/render_thread_impl.h
@@ -18,7 +18,7 @@
 #include "base/threading/thread_checker.h"
 #include "base/timer/timer.h"
 #include "build/build_config.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/content_export.h"
 #include "content/common/frame_replication_state.h"
 #include "content/common/gpu/client/gpu_channel_host.h"
@@ -110,6 +110,12 @@ class VideoCaptureImplManager;
 class WebGraphicsContext3DCommandBufferImpl;
 class WebRTCIdentityService;
 
+#if defined(COMPILER_MSVC)
+// See explanation for other RenderViewHostImpl which is the same issue.
+#pragma warning(push)
+#pragma warning(disable: 4250)
+#endif
+
 // The RenderThreadImpl class represents a background thread where RenderView
 // instances live.  The RenderThread supports an API that is used by its
 // consumer to talk indirectly to the RenderViews and supporting objects.
@@ -121,7 +127,7 @@ class WebRTCIdentityService;
 // The routing IDs correspond to RenderView instances.
 class CONTENT_EXPORT RenderThreadImpl
     : public RenderThread,
-      public ChildThread,
+      public ChildThreadImpl,
       public GpuChannelHostFactory,
       NON_EXPORTED_BASE(public CompositorDependencies) {
  public:
@@ -175,10 +181,6 @@ class CONTENT_EXPORT RenderThreadImpl
   int PostTaskToAllWebWorkers(const base::Closure& closure) override;
   bool ResolveProxy(const GURL& url, std::string* proxy_list) override;
   base::WaitableEvent* GetShutdownEvent() override;
-#if defined(OS_WIN)
-  virtual void PreCacheFont(const LOGFONT& log_font) override;
-  virtual void ReleaseCachedFonts() override;
-#endif
   ServiceRegistry* GetServiceRegistry() override;
 
   // CompositorDependencies implementation.
@@ -625,6 +627,10 @@ class CONTENT_EXPORT RenderThreadImpl
   DISALLOW_COPY_AND_ASSIGN(RenderThreadImpl);
 };
 
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)
+#endif
+
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_RENDER_THREAD_IMPL_H_
diff --git a/content/renderer/render_thread_impl_browsertest.cc b/content/renderer/render_thread_impl_browsertest.cc
index 3e4a795..39bf764 100644
--- a/content/renderer/render_thread_impl_browsertest.cc
+++ b/content/renderer/render_thread_impl_browsertest.cc
@@ -77,6 +77,12 @@ class TestTaskCounter : public base::SingleThreadTaskRunner {
   int count_;
 };
 
+#if defined(COMPILER_MSVC)
+// See explanation for other RenderViewHostImpl which is the same issue.
+#pragma warning(push)
+#pragma warning(disable: 4250)
+#endif
+
 class RenderThreadImplForTest : public RenderThreadImpl {
  public:
   RenderThreadImplForTest(const std::string& channel_id,
@@ -91,12 +97,16 @@ class RenderThreadImplForTest : public RenderThreadImpl {
     RenderThreadImpl::SetResourceDispatchTaskQueue(test_task_counter_);
   }
 
-  using ChildThread::OnMessageReceived;
+  using ChildThreadImpl::OnMessageReceived;
 
  private:
   scoped_refptr<TestTaskCounter> test_task_counter_;
 };
 
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)
+#endif
+
 void QuitTask(base::MessageLoop* message_loop) {
   message_loop->QuitWhenIdle();
 }
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 3be3eb3..8831340 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -35,7 +35,6 @@
 #include "content/child/appcache/appcache_dispatcher.h"
 #include "content/child/appcache/web_application_cache_host_impl.h"
 #include "content/child/child_shared_bitmap_manager.h"
-#include "content/child/child_thread.h"
 #include "content/child/npapi/webplugin_delegate_impl.h"
 #include "content/child/request_extra_data.h"
 #include "content/child/webmessageportchannel_impl.h"
diff --git a/content/renderer/renderer_blink_platform_impl.cc b/content/renderer/renderer_blink_platform_impl.cc
index 2894dc6..1fcf5bf 100644
--- a/content/renderer/renderer_blink_platform_impl.cc
+++ b/content/renderer/renderer_blink_platform_impl.cc
@@ -245,10 +245,10 @@ RendererBlinkPlatformImpl::RendererBlinkPlatformImpl(
   }
 
   // ChildThread may not exist in some tests.
-  if (ChildThread::current()) {
-    sync_message_filter_ = ChildThread::current()->sync_message_filter();
-    thread_safe_sender_ = ChildThread::current()->thread_safe_sender();
-    quota_message_filter_ = ChildThread::current()->quota_message_filter();
+  if (ChildThreadImpl::current()) {
+    sync_message_filter_ = ChildThreadImpl::current()->sync_message_filter();
+    thread_safe_sender_ = ChildThreadImpl::current()->thread_safe_sender();
+    quota_message_filter_ = ChildThreadImpl::current()->quota_message_filter();
     blob_registry_.reset(new WebBlobRegistryImpl(thread_safe_sender_.get()));
     web_idb_factory_.reset(new WebIDBFactoryImpl(thread_safe_sender_.get()));
     web_database_observer_impl_.reset(
diff --git a/content/renderer/renderer_clipboard_delegate.cc b/content/renderer/renderer_clipboard_delegate.cc
index b8d0b0c..0ed03f6 100644
--- a/content/renderer/renderer_clipboard_delegate.cc
+++ b/content/renderer/renderer_clipboard_delegate.cc
@@ -143,7 +143,7 @@ bool RendererClipboardDelegate::WriteImage(ui::ClipboardType clipboard_type,
 
     // Allocate a shared memory buffer to hold the bitmap bits.
     uint32 buf_size = checked_buf_size.ValueOrDie();
-    shared_buf = ChildThread::current()->AllocateSharedMemory(buf_size);
+    shared_buf = ChildThreadImpl::current()->AllocateSharedMemory(buf_size);
     if (!shared_buf)
       return false;
     if (!shared_buf->Map(buf_size))
diff --git a/content/renderer/service_worker/embedded_worker_context_client.cc b/content/renderer/service_worker/embedded_worker_context_client.cc
index d04fc06..2c50e5c 100644
--- a/content/renderer/service_worker/embedded_worker_context_client.cc
+++ b/content/renderer/service_worker/embedded_worker_context_client.cc
@@ -103,7 +103,7 @@ EmbeddedWorkerContextClient::EmbeddedWorkerContextClient(
       service_worker_scope_(service_worker_scope),
       script_url_(script_url),
       worker_devtools_agent_route_id_(worker_devtools_agent_route_id),
-      sender_(ChildThread::current()->thread_safe_sender()),
+      sender_(ChildThreadImpl::current()->thread_safe_sender()),
       main_thread_proxy_(base::MessageLoopProxy::current()),
       weak_factory_(this) {
   TRACE_EVENT_ASYNC_BEGIN0("ServiceWorker",
diff --git a/content/renderer/service_worker/embedded_worker_context_message_filter.cc b/content/renderer/service_worker/embedded_worker_context_message_filter.cc
index cbc141d..4999b38 100644
--- a/content/renderer/service_worker/embedded_worker_context_message_filter.cc
+++ b/content/renderer/service_worker/embedded_worker_context_message_filter.cc
@@ -5,7 +5,7 @@
 #include "content/renderer/service_worker/embedded_worker_context_message_filter.h"
 
 #include "base/message_loop/message_loop_proxy.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/child/worker_thread_task_runner.h"
 #include "content/renderer/service_worker/embedded_worker_context_client.h"
@@ -15,7 +15,7 @@ namespace content {
 
 EmbeddedWorkerContextMessageFilter::EmbeddedWorkerContextMessageFilter()
     : main_thread_loop_proxy_(base::MessageLoopProxy::current()),
-      thread_safe_sender_(ChildThread::current()->thread_safe_sender()) {}
+      thread_safe_sender_(ChildThreadImpl::current()->thread_safe_sender()) {}
 
 EmbeddedWorkerContextMessageFilter::~EmbeddedWorkerContextMessageFilter() {}
 
diff --git a/content/renderer/service_worker/embedded_worker_devtools_agent.cc b/content/renderer/service_worker/embedded_worker_devtools_agent.cc
index 791a2ca..e1c640a 100644
--- a/content/renderer/service_worker/embedded_worker_devtools_agent.cc
+++ b/content/renderer/service_worker/embedded_worker_devtools_agent.cc
@@ -4,7 +4,6 @@
 
 #include "content/renderer/service_worker/embedded_worker_devtools_agent.h"
 
-#include "content/child/child_thread.h"
 #include "content/common/devtools_messages.h"
 #include "content/renderer/render_thread_impl.h"
 #include "third_party/WebKit/public/platform/WebCString.h"
diff --git a/content/renderer/shared_worker/embedded_shared_worker_stub.cc b/content/renderer/shared_worker/embedded_shared_worker_stub.cc
index d026cec..121831f 100644
--- a/content/renderer/shared_worker/embedded_shared_worker_stub.cc
+++ b/content/renderer/shared_worker/embedded_shared_worker_stub.cc
@@ -168,7 +168,7 @@ blink::WebWorkerPermissionClientProxy*
       GURL(origin.toString()),
       origin.isUnique(),
       route_id_,
-      ChildThread::current()->thread_safe_sender());
+      ChildThreadImpl::current()->thread_safe_sender());
 }
 
 void EmbeddedSharedWorkerStub::sendDevToolsMessage(
diff --git a/content/renderer/shared_worker_repository.cc b/content/renderer/shared_worker_repository.cc
index a883464..46dcb91 100644
--- a/content/renderer/shared_worker_repository.cc
+++ b/content/renderer/shared_worker_repository.cc
@@ -4,7 +4,7 @@
 
 #include "content/renderer/shared_worker_repository.h"
 
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/view_messages.h"
 #include "content/renderer/render_frame_impl.h"
 #include "content/renderer/websharedworker_proxy.h"
@@ -39,7 +39,7 @@ SharedWorkerRepository::createSharedWorkerConnector(
   if (route_id == MSG_ROUTING_NONE)
     return NULL;
   documents_with_workers_.insert(document_id);
-  return new WebSharedWorkerProxy(ChildThread::current()->GetRouter(),
+  return new WebSharedWorkerProxy(ChildThreadImpl::current()->GetRouter(),
                                   document_id,
                                   route_id,
                                   params.render_frame_route_id);
diff --git a/content/utility/utility_thread_impl.cc b/content/utility/utility_thread_impl.cc
index 32f9814..26af2b1 100644
--- a/content/utility/utility_thread_impl.cc
+++ b/content/utility/utility_thread_impl.cc
@@ -40,7 +40,7 @@ UtilityThreadImpl::UtilityThreadImpl() : single_process_(false) {
 }
 
 UtilityThreadImpl::UtilityThreadImpl(const std::string& channel_name)
-    : ChildThread(Options(channel_name, false)),
+    : ChildThreadImpl(Options(channel_name, false)),
       single_process_(true) {
   Init();
 }
@@ -49,16 +49,12 @@ UtilityThreadImpl::~UtilityThreadImpl() {
 }
 
 void UtilityThreadImpl::Shutdown() {
-  ChildThread::Shutdown();
+  ChildThreadImpl::Shutdown();
 
   if (!single_process_)
     blink::shutdown();
 }
 
-bool UtilityThreadImpl::Send(IPC::Message* msg) {
-  return ChildThread::Send(msg);
-}
-
 void UtilityThreadImpl::ReleaseProcessIfNeeded() {
   if (batch_mode_)
     return;
@@ -74,18 +70,6 @@ void UtilityThreadImpl::ReleaseProcessIfNeeded() {
   }
 }
 
-#if defined(OS_WIN)
-
-void UtilityThreadImpl::PreCacheFont(const LOGFONT& log_font) {
-  Send(new ChildProcessHostMsg_PreCacheFont(log_font));
-}
-
-void UtilityThreadImpl::ReleaseCachedFonts() {
-  Send(new ChildProcessHostMsg_ReleaseCachedFonts());
-}
-
-#endif  // OS_WIN
-
 void UtilityThreadImpl::Init() {
   batch_mode_ = false;
   ChildProcess::current()->AddRefProcess();
diff --git a/content/utility/utility_thread_impl.h b/content/utility/utility_thread_impl.h
index 5b186fc..043aea9 100644
--- a/content/utility/utility_thread_impl.h
+++ b/content/utility/utility_thread_impl.h
@@ -10,7 +10,7 @@
 
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
-#include "content/child/child_thread.h"
+#include "content/child/child_thread_impl.h"
 #include "content/common/content_export.h"
 #include "content/public/utility/utility_thread.h"
 
@@ -21,9 +21,15 @@ class FilePath;
 namespace content {
 class BlinkPlatformImpl;
 
+#if defined(COMPILER_MSVC)
+// See explanation for other RenderViewHostImpl which is the same issue.
+#pragma warning(push)
+#pragma warning(disable: 4250)
+#endif
+
 // This class represents the background thread where the utility task runs.
 class UtilityThreadImpl : public UtilityThread,
-                          public ChildThread {
+                          public ChildThreadImpl {
  public:
   UtilityThreadImpl();
   // Constructor that's used when running in single process mode.
@@ -31,12 +37,7 @@ class UtilityThreadImpl : public UtilityThread,
   ~UtilityThreadImpl() override;
   void Shutdown() override;
 
-  bool Send(IPC::Message* msg) override;
   void ReleaseProcessIfNeeded() override;
-#if defined(OS_WIN)
-  virtual void PreCacheFont(const LOGFONT& log_font) override;
-  virtual void ReleaseCachedFonts() override;
-#endif
 
  private:
   void Init();
@@ -63,6 +64,10 @@ class UtilityThreadImpl : public UtilityThread,
   DISALLOW_COPY_AND_ASSIGN(UtilityThreadImpl);
 };
 
+#if defined(COMPILER_MSVC)
+#pragma warning(pop)
+#endif
+
 }  // namespace content
 
 #endif  // CONTENT_UTILITY_UTILITY_THREAD_IMPL_H_