Move WorkerTaskRunner observer interface to WorkerThread.

This moves WorkerTaskRunner::Observer to WorkerThread::Observer, and renames
WorkerTaskRunner::Add/RemoveStopObserver to
WorkerThread::DidStartCurrentWorkerThread/WillStopCurrentWorkerThread.
Some other code made sense to shuffle around while doing so.

BUG=501569
R=kinuko@chromium.org

Review URL: https://codereview.chromium.org/1307643006

Cr-Commit-Position: refs/heads/master@{#347479}

36 files changed, 287 insertions, 254 deletions

diff --git a/content/child/background_sync/background_sync_provider_thread_proxy.cc b/content/child/background_sync/background_sync_provider_thread_proxy.cc
index af0e786..3d735fb 100644
--- a/content/child/background_sync/background_sync_provider_thread_proxy.cc
+++ b/content/child/background_sync/background_sync_provider_thread_proxy.cc
@@ -85,7 +85,7 @@ BackgroundSyncProviderThreadProxy::GetThreadInstance(
   if (g_sync_provider_tls.Pointer()->Get())
     return g_sync_provider_tls.Pointer()->Get();
 
-  if (!WorkerTaskRunner::Instance()->CurrentWorkerId()) {
+  if (!WorkerThread::GetCurrentId()) {
     // This could happen if GetThreadInstance is called very late (say by a
     // garbage collected SyncRegistration).
     return nullptr;
@@ -94,7 +94,7 @@ BackgroundSyncProviderThreadProxy::GetThreadInstance(
   BackgroundSyncProviderThreadProxy* instance =
       new BackgroundSyncProviderThreadProxy(main_thread_task_runner,
                                             sync_provider);
-  WorkerTaskRunner::Instance()->AddStopObserver(instance);
+  WorkerThread::AddObserver(instance);
   return instance;
 }
 
@@ -108,12 +108,12 @@ void BackgroundSyncProviderThreadProxy::registerBackgroundSync(
   DCHECK(callbacks);
   main_thread_task_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&BackgroundSyncProvider::registerBackgroundSync,
-                 base::Unretained(sync_provider_), options,
-                 service_worker_registration, requested_from_service_worker,
-                 new CallbackThreadAdapter<blink::WebSyncRegistrationCallbacks>(
-                     make_scoped_ptr(callbacks),
-                     WorkerTaskRunner::Instance()->CurrentWorkerId())));
+      base::Bind(
+          &BackgroundSyncProvider::registerBackgroundSync,
+          base::Unretained(sync_provider_), options,
+          service_worker_registration, requested_from_service_worker,
+          new CallbackThreadAdapter<blink::WebSyncRegistrationCallbacks>(
+              make_scoped_ptr(callbacks), WorkerThread::GetCurrentId())));
 }
 
 void BackgroundSyncProviderThreadProxy::unregisterBackgroundSync(
@@ -133,8 +133,7 @@ void BackgroundSyncProviderThreadProxy::unregisterBackgroundSync(
           // for thread-safety.
           static_cast<base::string16>(tag), service_worker_registration,
           new CallbackThreadAdapter<blink::WebSyncUnregistrationCallbacks>(
-              make_scoped_ptr(callbacks),
-              WorkerTaskRunner::Instance()->CurrentWorkerId())));
+              make_scoped_ptr(callbacks), WorkerThread::GetCurrentId())));
 }
 
 void BackgroundSyncProviderThreadProxy::getRegistration(
@@ -146,14 +145,14 @@ void BackgroundSyncProviderThreadProxy::getRegistration(
   DCHECK(callbacks);
   main_thread_task_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&BackgroundSyncProvider::getRegistration,
-                 base::Unretained(sync_provider_), periodicity,
-                 // We cast WebString to string16 before crossing threads
-                 // for thread-safety.
-                 static_cast<base::string16>(tag), service_worker_registration,
-                 new CallbackThreadAdapter<blink::WebSyncRegistrationCallbacks>(
-                     make_scoped_ptr(callbacks),
-                     WorkerTaskRunner::Instance()->CurrentWorkerId())));
+      base::Bind(
+          &BackgroundSyncProvider::getRegistration,
+          base::Unretained(sync_provider_), periodicity,
+          // We cast WebString to string16 before crossing threads
+          // for thread-safety.
+          static_cast<base::string16>(tag), service_worker_registration,
+          new CallbackThreadAdapter<blink::WebSyncRegistrationCallbacks>(
+              make_scoped_ptr(callbacks), WorkerThread::GetCurrentId())));
 }
 
 void BackgroundSyncProviderThreadProxy::getRegistrations(
@@ -169,8 +168,7 @@ void BackgroundSyncProviderThreadProxy::getRegistrations(
           base::Unretained(sync_provider_), periodicity,
           service_worker_registration,
           new CallbackThreadAdapter<blink::WebSyncGetRegistrationsCallbacks>(
-              make_scoped_ptr(callbacks),
-              WorkerTaskRunner::Instance()->CurrentWorkerId())));
+              make_scoped_ptr(callbacks), WorkerThread::GetCurrentId())));
 }
 
 void BackgroundSyncProviderThreadProxy::getPermissionStatus(
@@ -186,11 +184,10 @@ void BackgroundSyncProviderThreadProxy::getPermissionStatus(
           base::Unretained(sync_provider_), periodicity,
           service_worker_registration,
           new CallbackThreadAdapter<blink::WebSyncGetPermissionStatusCallbacks>(
-              make_scoped_ptr(callbacks),
-              WorkerTaskRunner::Instance()->CurrentWorkerId())));
+              make_scoped_ptr(callbacks), WorkerThread::GetCurrentId())));
 }
 
-void BackgroundSyncProviderThreadProxy::OnWorkerRunLoopStopped() {
+void BackgroundSyncProviderThreadProxy::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/background_sync/background_sync_provider_thread_proxy.h b/content/child/background_sync/background_sync_provider_thread_proxy.h
index 048c68f..7b6e8fe 100644
--- a/content/child/background_sync/background_sync_provider_thread_proxy.h
+++ b/content/child/background_sync/background_sync_provider_thread_proxy.h
@@ -7,6 +7,7 @@
 
 #include "base/macros.h"
 #include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/modules/background_sync/WebSyncProvider.h"
 
 namespace base {
@@ -25,7 +26,7 @@ class BackgroundSyncProvider;
 // call the WebSyncProvider methods, and wrapping the callbacks passed in with
 // code to switch back to the original calling thread.
 class BackgroundSyncProviderThreadProxy : public blink::WebSyncProvider,
-                                          public WorkerTaskRunner::Observer {
+                                          public WorkerThread::Observer {
  public:
   static BackgroundSyncProviderThreadProxy* GetThreadInstance(
       base::SingleThreadTaskRunner* main_thread_task_runner,
@@ -57,8 +58,8 @@ class BackgroundSyncProviderThreadProxy : public blink::WebSyncProvider,
       blink::WebServiceWorkerRegistration* service_worker_registration,
       blink::WebSyncGetPermissionStatusCallbacks* callbacks);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
  private:
   BackgroundSyncProviderThreadProxy(
diff --git a/content/child/blink_platform_impl.cc b/content/child/blink_platform_impl.cc
index 1ff9675..4e7615f 100644
--- a/content/child/blink_platform_impl.cc
+++ b/content/child/blink_platform_impl.cc
@@ -1144,12 +1144,15 @@ blink::WebGestureCurve* BlinkPlatformImpl::createFlingAnimationCurve(
 
 void BlinkPlatformImpl::didStartWorkerRunLoop() {
   WorkerTaskRunner* worker_task_runner = WorkerTaskRunner::Instance();
-  worker_task_runner->OnWorkerRunLoopStarted();
+  worker_task_runner->DidStartWorkerRunLoop();
 }
 
 void BlinkPlatformImpl::didStopWorkerRunLoop() {
+  // TODO(kalman): blink::Platform::didStopWorkerRunLoop should be called
+  // willStopWorkerRunLoop, because at this point the run loop hasn't been
+  // stopped. WillStopWorkerRunLoop is the correct name.
   WorkerTaskRunner* worker_task_runner = WorkerTaskRunner::Instance();
-  worker_task_runner->OnWorkerRunLoopStopped();
+  worker_task_runner->WillStopWorkerRunLoop();
 }
 
 blink::WebCrypto* BlinkPlatformImpl::crypto() {
diff --git a/content/child/fileapi/webfilesystem_impl.cc b/content/child/fileapi/webfilesystem_impl.cc
index 9aba734..39f7481 100644
--- a/content/child/fileapi/webfilesystem_impl.cc
+++ b/content/child/fileapi/webfilesystem_impl.cc
@@ -382,13 +382,13 @@ WebFileSystemImpl* WebFileSystemImpl::ThreadSpecificInstance(
     return g_webfilesystem_tls.Pointer()->Get();
   WebFileSystemImpl* filesystem =
       new WebFileSystemImpl(main_thread_task_runner);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(filesystem);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(filesystem);
   return filesystem;
 }
 
 void WebFileSystemImpl::DeleteThreadSpecificInstance() {
-  DCHECK(!WorkerTaskRunner::Instance()->CurrentWorkerId());
+  DCHECK(!WorkerThread::GetCurrentId());
   if (g_webfilesystem_tls.Pointer()->Get())
     delete g_webfilesystem_tls.Pointer()->Get();
 }
@@ -404,7 +404,7 @@ WebFileSystemImpl::~WebFileSystemImpl() {
   g_webfilesystem_tls.Pointer()->Set(NULL);
 }
 
-void WebFileSystemImpl::OnWorkerRunLoopStopped() {
+void WebFileSystemImpl::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/fileapi/webfilesystem_impl.h b/content/child/fileapi/webfilesystem_impl.h
index 66c7826..e9d6cc8 100644
--- a/content/child/fileapi/webfilesystem_impl.h
+++ b/content/child/fileapi/webfilesystem_impl.h
@@ -11,7 +11,7 @@
 #include "base/compiler_specific.h"
 #include "base/memory/ref_counted.h"
 #include "base/threading/non_thread_safe.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/WebFileSystem.h"
 
 namespace base {
@@ -28,7 +28,7 @@ class WebFileWriterClient;
 namespace content {
 
 class WebFileSystemImpl : public blink::WebFileSystem,
-                          public WorkerTaskRunner::Observer,
+                          public WorkerThread::Observer,
                           public base::NonThreadSafe {
  public:
   class WaitableCallbackResults;
@@ -41,7 +41,7 @@ class WebFileSystemImpl : public blink::WebFileSystem,
           main_thread_task_runner);
 
   // Deletes thread-specific instance (if exists). For workers it deletes
-  // itself in OnWorkerRunLoopStopped(), but for an instance created on the
+  // itself in WillStopCurrentWorkerThread(), but for an instance created on the
   // main thread this method must be called.
   static void DeleteThreadSpecificInstance();
 
@@ -50,8 +50,8 @@ class WebFileSystemImpl : public blink::WebFileSystem,
           main_thread_task_runner);
   virtual ~WebFileSystemImpl();
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   // WebFileSystem implementation.
   virtual void openFileSystem(
diff --git a/content/child/fileapi/webfilewriter_impl.cc b/content/child/fileapi/webfilewriter_impl.cc
index ef16def..701e706 100644
--- a/content/child/fileapi/webfilewriter_impl.cc
+++ b/content/child/fileapi/webfilewriter_impl.cc
@@ -9,7 +9,7 @@
 #include "base/thread_task_runner_handle.h"
 #include "content/child/child_thread_impl.h"
 #include "content/child/fileapi/file_system_dispatcher.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 
 namespace content {
 
@@ -32,7 +32,7 @@ class WebFileWriterImpl::WriterBridge
  public:
   WriterBridge(WebFileWriterImpl::Type type)
       : request_id_(0),
-        running_on_worker_(WorkerTaskRunner::Instance()->CurrentWorkerId() > 0),
+        running_on_worker_(WorkerThread::GetCurrentId() > 0),
         task_runner_(running_on_worker_ ? base::ThreadTaskRunnerHandle::Get()
                                         : nullptr),
         written_bytes_(0) {
diff --git a/content/child/geofencing/geofencing_dispatcher.cc b/content/child/geofencing/geofencing_dispatcher.cc
index e067008..ae2f9e2 100644
--- a/content/child/geofencing/geofencing_dispatcher.cc
+++ b/content/child/geofencing/geofencing_dispatcher.cc
@@ -28,7 +28,7 @@ base::LazyInstance<base::ThreadLocalPointer<void>>::Leaky g_dispatcher_tls =
 void* const kHasBeenDeleted = reinterpret_cast<void*>(0x1);
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 }  // namespace
@@ -145,8 +145,8 @@ GeofencingDispatcher* GeofencingDispatcher::GetOrCreateThreadSpecificInstance(
 
   GeofencingDispatcher* dispatcher =
       new GeofencingDispatcher(thread_safe_sender);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
@@ -217,7 +217,7 @@ void GeofencingDispatcher::OnGetRegisteredRegionsComplete(
   get_registered_regions_requests_.Remove(request_id);
 }
 
-void GeofencingDispatcher::OnWorkerRunLoopStopped() {
+void GeofencingDispatcher::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/geofencing/geofencing_dispatcher.h b/content/child/geofencing/geofencing_dispatcher.h
index 269dfe7..bd12543 100644
--- a/content/child/geofencing/geofencing_dispatcher.h
+++ b/content/child/geofencing/geofencing_dispatcher.h
@@ -5,11 +5,14 @@
 #ifndef CONTENT_CHILD_GEOFENCING_GEOFENCING_DISPATCHER_H_
 #define CONTENT_CHILD_GEOFENCING_GEOFENCING_DISPATCHER_H_
 
+#include <map>
+#include <string>
+
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/geofencing_types.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/WebGeofencingProvider.h"
 
 namespace base {
@@ -24,7 +27,7 @@ class Message;
 namespace content {
 class ThreadSafeSender;
 
-class GeofencingDispatcher : public WorkerTaskRunner::Observer {
+class GeofencingDispatcher : public WorkerThread::Observer {
  public:
   explicit GeofencingDispatcher(ThreadSafeSender* sender);
   ~GeofencingDispatcher() override;
@@ -76,8 +79,8 @@ class GeofencingDispatcher : public WorkerTaskRunner::Observer {
       GeofencingStatus status,
       const std::map<std::string, blink::WebCircularGeofencingRegion>& regions);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   scoped_refptr<ThreadSafeSender> thread_safe_sender_;
   IDMap<blink::WebGeofencingCallbacks, IDMapOwnPointer>
diff --git a/content/child/indexed_db/indexed_db_dispatcher.cc b/content/child/indexed_db/indexed_db_dispatcher.cc
index 3862e3b..beecc89 100644
--- a/content/child/indexed_db/indexed_db_dispatcher.cc
+++ b/content/child/indexed_db/indexed_db_dispatcher.cc
@@ -73,12 +73,14 @@ IndexedDBDispatcher* IndexedDBDispatcher::ThreadSpecificInstance(
     return g_idb_dispatcher_tls.Pointer()->Get();
 
   IndexedDBDispatcher* dispatcher = new IndexedDBDispatcher(thread_safe_sender);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
-void IndexedDBDispatcher::OnWorkerRunLoopStopped() { delete this; }
+void IndexedDBDispatcher::WillStopCurrentWorkerThread() {
+  delete this;
+}
 
 WebIDBMetadata IndexedDBDispatcher::ConvertMetadata(
     const IndexedDBDatabaseMetadata& idb_metadata) {
diff --git a/content/child/indexed_db/indexed_db_dispatcher.h b/content/child/indexed_db/indexed_db_dispatcher.h
index 854878d..67a11ab 100644
--- a/content/child/indexed_db/indexed_db_dispatcher.h
+++ b/content/child/indexed_db/indexed_db_dispatcher.h
@@ -13,9 +13,9 @@
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/nullable_string16.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/content_export.h"
 #include "content/common/indexed_db/indexed_db_constants.h"
+#include "content/public/child/worker_thread.h"
 #include "ipc/ipc_sync_message_filter.h"
 #include "third_party/WebKit/public/platform/WebBlobInfo.h"
 #include "third_party/WebKit/public/platform/modules/indexeddb/WebIDBCallbacks.h"
@@ -44,7 +44,7 @@ class ThreadSafeSender;
 
 // Handle the indexed db related communication for this context thread - the
 // main thread and each worker thread have their own copies.
-class CONTENT_EXPORT IndexedDBDispatcher : public WorkerTaskRunner::Observer {
+class CONTENT_EXPORT IndexedDBDispatcher : public WorkerThread::Observer {
  public:
   // Constructor made public to allow RenderThreadImpl to own a copy without
   // failing a NOTREACHED in ThreadSpecificInstance in tests that instantiate
@@ -58,8 +58,8 @@ class CONTENT_EXPORT IndexedDBDispatcher : public WorkerTaskRunner::Observer {
   static IndexedDBDispatcher* ThreadSpecificInstance(
       ThreadSafeSender* thread_safe_sender);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   static blink::WebIDBMetadata ConvertMetadata(
       const IndexedDBDatabaseMetadata& idb_metadata);
@@ -188,9 +188,7 @@ class CONTENT_EXPORT IndexedDBDispatcher : public WorkerTaskRunner::Observer {
 
   enum { kAllCursors = -1 };
 
-  static int32 CurrentWorkerId() {
-    return WorkerTaskRunner::Instance()->CurrentWorkerId();
-  }
+  static int32 CurrentWorkerId() { return WorkerThread::GetCurrentId(); }
 
   template <typename T>
   void init_params(T* params, blink::WebIDBCallbacks* callbacks_ptr) {
diff --git a/content/child/navigator_connect/service_port_dispatcher_impl.cc b/content/child/navigator_connect/service_port_dispatcher_impl.cc
index ec74025..977f2b9 100644
--- a/content/child/navigator_connect/service_port_dispatcher_impl.cc
+++ b/content/child/navigator_connect/service_port_dispatcher_impl.cc
@@ -46,17 +46,17 @@ void ServicePortDispatcherImpl::Create(
 }
 
 ServicePortDispatcherImpl::~ServicePortDispatcherImpl() {
-  WorkerTaskRunner::Instance()->RemoveStopObserver(this);
+  WorkerThread::RemoveObserver(this);
 }
 
 ServicePortDispatcherImpl::ServicePortDispatcherImpl(
     base::WeakPtr<blink::WebServiceWorkerContextProxy> proxy,
     mojo::InterfaceRequest<ServicePortDispatcher> request)
     : binding_(this, request.Pass()), proxy_(proxy) {
-  WorkerTaskRunner::Instance()->AddStopObserver(this);
+  WorkerThread::AddObserver(this);
 }
 
-void ServicePortDispatcherImpl::OnWorkerRunLoopStopped() {
+void ServicePortDispatcherImpl::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/navigator_connect/service_port_dispatcher_impl.h b/content/child/navigator_connect/service_port_dispatcher_impl.h
index 079e077..a03ae71 100644
--- a/content/child/navigator_connect/service_port_dispatcher_impl.h
+++ b/content/child/navigator_connect/service_port_dispatcher_impl.h
@@ -7,8 +7,8 @@
 
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/service_port_service.mojom.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/mojo/src/mojo/public/cpp/bindings/strong_binding.h"
 
 namespace blink {
@@ -23,7 +23,7 @@ namespace content {
 // channel and the lifetime of the worker thread. If either the channel is
 // disconnected or the worker thread stops the instance deletes itself.
 class ServicePortDispatcherImpl : public ServicePortDispatcher,
-                                  public WorkerTaskRunner::Observer {
+                                  public WorkerThread::Observer {
  public:
   static void Create(base::WeakPtr<blink::WebServiceWorkerContextProxy> proxy,
                      mojo::InterfaceRequest<ServicePortDispatcher> request);
@@ -35,8 +35,8 @@ class ServicePortDispatcherImpl : public ServicePortDispatcher,
       base::WeakPtr<blink::WebServiceWorkerContextProxy> proxy,
       mojo::InterfaceRequest<ServicePortDispatcher> request);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   // ServicePortDispatcher implementation.
   void Connect(const mojo::String& target_url,
diff --git a/content/child/notifications/notification_manager.cc b/content/child/notifications/notification_manager.cc
index 19ac1c3..920cba7 100644
--- a/content/child/notifications/notification_manager.cc
+++ b/content/child/notifications/notification_manager.cc
@@ -15,7 +15,6 @@
 #include "content/child/notifications/notification_dispatcher.h"
 #include "content/child/service_worker/web_service_worker_registration_impl.h"
 #include "content/child/thread_safe_sender.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/notification_constants.h"
 #include "content/public/common/platform_notification_data.h"
 #include "third_party/WebKit/public/platform/WebSecurityOrigin.h"
@@ -28,7 +27,7 @@ namespace content {
 namespace {
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 }  // namespace
@@ -60,11 +59,11 @@ NotificationManager* NotificationManager::ThreadSpecificInstance(
   NotificationManager* manager = new NotificationManager(
       thread_safe_sender, main_thread_task_runner, notification_dispatcher);
   if (CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(manager);
+    WorkerThread::AddObserver(manager);
   return manager;
 }
 
-void NotificationManager::OnWorkerRunLoopStopped() {
+void NotificationManager::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/notifications/notification_manager.h b/content/child/notifications/notification_manager.h
index 5aed100..962ba35 100644
--- a/content/child/notifications/notification_manager.h
+++ b/content/child/notifications/notification_manager.h
@@ -14,8 +14,8 @@
 #include "base/single_thread_task_runner.h"
 #include "content/child/notifications/notification_dispatcher.h"
 #include "content/child/notifications/pending_notifications_tracker.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/platform_notification_messages.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/modules/notifications/WebNotificationManager.h"
 
 class SkBitmap;
@@ -26,7 +26,7 @@ struct PlatformNotificationData;
 class ThreadSafeSender;
 
 class NotificationManager : public blink::WebNotificationManager,
-                            public WorkerTaskRunner::Observer {
+                            public WorkerThread::Observer {
  public:
   ~NotificationManager() override;
 
@@ -37,8 +37,8 @@ class NotificationManager : public blink::WebNotificationManager,
       base::SingleThreadTaskRunner* main_thread_task_runner,
       NotificationDispatcher* notification_dispatcher);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   // blink::WebNotificationManager implementation.
   virtual void show(const blink::WebSecurityOrigin& origin,
diff --git a/content/child/permissions/permission_dispatcher_thread_proxy.cc b/content/child/permissions/permission_dispatcher_thread_proxy.cc
index 01c4a8c..b2af016 100644
--- a/content/child/permissions/permission_dispatcher_thread_proxy.cc
+++ b/content/child/permissions/permission_dispatcher_thread_proxy.cc
@@ -11,7 +11,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_local.h"
 #include "content/child/permissions/permission_dispatcher.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/WebURL.h"
 #include "third_party/WebKit/public/platform/modules/permissions/WebPermissionObserver.h"
 
@@ -37,8 +37,8 @@ PermissionDispatcherThreadProxy::GetThreadInstance(
   PermissionDispatcherThreadProxy* instance =
       new PermissionDispatcherThreadProxy(main_thread_task_runner,
                                         permission_dispatcher);
-  DCHECK(WorkerTaskRunner::Instance()->CurrentWorkerId());
-  WorkerTaskRunner::Instance()->AddStopObserver(instance);
+  DCHECK(WorkerThread::GetCurrentId());
+  WorkerThread::AddObserver(instance);
   return instance;
 }
 
@@ -59,13 +59,10 @@ void PermissionDispatcherThreadProxy::queryPermission(
     const blink::WebURL& origin,
     blink::WebPermissionCallback* callback) {
   main_thread_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&PermissionDispatcher::QueryPermissionForWorker,
-                 base::Unretained(permission_dispatcher_),
-                 type,
-                 origin.string().utf8(),
-                 base::Unretained(callback),
-                 WorkerTaskRunner::Instance()->CurrentWorkerId()));
+      FROM_HERE, base::Bind(&PermissionDispatcher::QueryPermissionForWorker,
+                            base::Unretained(permission_dispatcher_), type,
+                            origin.string().utf8(), base::Unretained(callback),
+                            WorkerThread::GetCurrentId()));
 }
 
 void PermissionDispatcherThreadProxy::requestPermission(
@@ -73,13 +70,10 @@ void PermissionDispatcherThreadProxy::requestPermission(
     const blink::WebURL& origin,
     blink::WebPermissionCallback* callback) {
   main_thread_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&PermissionDispatcher::RequestPermissionForWorker,
-                 base::Unretained(permission_dispatcher_),
-                 type,
-                 origin.string().utf8(),
-                 base::Unretained(callback),
-                 WorkerTaskRunner::Instance()->CurrentWorkerId()));
+      FROM_HERE, base::Bind(&PermissionDispatcher::RequestPermissionForWorker,
+                            base::Unretained(permission_dispatcher_), type,
+                            origin.string().utf8(), base::Unretained(callback),
+                            WorkerThread::GetCurrentId()));
 }
 
 void PermissionDispatcherThreadProxy::requestPermissions(
@@ -87,13 +81,10 @@ void PermissionDispatcherThreadProxy::requestPermissions(
     const blink::WebURL& origin,
     blink::WebPermissionsCallback* callback) {
   main_thread_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&PermissionDispatcher::RequestPermissionsForWorker,
-                 base::Unretained(permission_dispatcher_),
-                 types,
-                 origin.string().utf8(),
-                 base::Unretained(callback),
-                 WorkerTaskRunner::Instance()->CurrentWorkerId()));
+      FROM_HERE, base::Bind(&PermissionDispatcher::RequestPermissionsForWorker,
+                            base::Unretained(permission_dispatcher_), types,
+                            origin.string().utf8(), base::Unretained(callback),
+                            WorkerThread::GetCurrentId()));
 }
 
 void PermissionDispatcherThreadProxy::revokePermission(
@@ -101,13 +92,10 @@ void PermissionDispatcherThreadProxy::revokePermission(
     const blink::WebURL& origin,
     blink::WebPermissionCallback* callback) {
   main_thread_task_runner_->PostTask(
-      FROM_HERE,
-      base::Bind(&PermissionDispatcher::RevokePermissionForWorker,
-                 base::Unretained(permission_dispatcher_),
-                 type,
-                 origin.string().utf8(),
-                 base::Unretained(callback),
-                 WorkerTaskRunner::Instance()->CurrentWorkerId()));
+      FROM_HERE, base::Bind(&PermissionDispatcher::RevokePermissionForWorker,
+                            base::Unretained(permission_dispatcher_), type,
+                            origin.string().utf8(), base::Unretained(callback),
+                            WorkerThread::GetCurrentId()));
 }
 
 void PermissionDispatcherThreadProxy::startListening(
@@ -119,16 +107,14 @@ void PermissionDispatcherThreadProxy::startListening(
 
   RegisterObserver(observer);
 
-  main_thread_task_runner_->PostTask(FROM_HERE,
-      base::Bind(&PermissionDispatcher::StartListeningForWorker,
-          base::Unretained(permission_dispatcher_),
-          type,
-          origin.string().utf8(),
-          WorkerTaskRunner::Instance()->CurrentWorkerId(),
+  main_thread_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &PermissionDispatcher::StartListeningForWorker,
+          base::Unretained(permission_dispatcher_), type,
+          origin.string().utf8(), WorkerThread::GetCurrentId(),
           base::Bind(&PermissionDispatcherThreadProxy::OnPermissionChanged,
-                     base::Unretained(this),
-                     type,
-                     origin.string().utf8(),
+                     base::Unretained(this), type, origin.string().utf8(),
                      base::Unretained(observer))));
 }
 
@@ -147,21 +133,18 @@ void PermissionDispatcherThreadProxy::OnPermissionChanged(
 
   observer->permissionChanged(type, status);
 
-  main_thread_task_runner_->PostTask(FROM_HERE,
-      base::Bind(&PermissionDispatcher::GetNextPermissionChangeForWorker,
-          base::Unretained(permission_dispatcher_),
-          type,
-          origin,
-          status,
-          WorkerTaskRunner::Instance()->CurrentWorkerId(),
+  main_thread_task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(
+          &PermissionDispatcher::GetNextPermissionChangeForWorker,
+          base::Unretained(permission_dispatcher_), type, origin, status,
+          WorkerThread::GetCurrentId(),
           base::Bind(&PermissionDispatcherThreadProxy::OnPermissionChanged,
-                     base::Unretained(this),
-                     type,
-                     origin,
+                     base::Unretained(this), type, origin,
                      base::Unretained(observer))));
 }
 
-void PermissionDispatcherThreadProxy::OnWorkerRunLoopStopped() {
+void PermissionDispatcherThreadProxy::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/permissions/permission_dispatcher_thread_proxy.h b/content/child/permissions/permission_dispatcher_thread_proxy.h
index d290367..180a261 100644
--- a/content/child/permissions/permission_dispatcher_thread_proxy.h
+++ b/content/child/permissions/permission_dispatcher_thread_proxy.h
@@ -9,7 +9,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "content/child/permissions/permission_observers_registry.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/modules/permissions/WebPermissionClient.h"
 
 namespace base {
@@ -23,10 +23,9 @@ class PermissionDispatcher;
 // PermissionDispatcherThreadProxy is a a proxy to the PermissionDispatcher for
 // callers running on a different thread than the main thread. There is one
 // instance of that class per thread.
-class PermissionDispatcherThreadProxy :
-    public blink::WebPermissionClient,
-    public PermissionObserversRegistry,
-    public WorkerTaskRunner::Observer {
+class PermissionDispatcherThreadProxy : public blink::WebPermissionClient,
+                                        public PermissionObserversRegistry,
+                                        public WorkerThread::Observer {
  public:
   static PermissionDispatcherThreadProxy* GetThreadInstance(
       base::SingleThreadTaskRunner* main_thread_task_runner,
@@ -51,8 +50,8 @@ class PermissionDispatcherThreadProxy :
                               blink::WebPermissionObserver* observer);
   virtual void stopListening(blink::WebPermissionObserver* observer);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
  private:
   PermissionDispatcherThreadProxy(
diff --git a/content/child/push_messaging/push_provider.cc b/content/child/push_messaging/push_provider.cc
index 0894601..ba82b0f 100644
--- a/content/child/push_messaging/push_provider.cc
+++ b/content/child/push_messaging/push_provider.cc
@@ -11,7 +11,6 @@
 #include "content/child/push_messaging/push_dispatcher.h"
 #include "content/child/service_worker/web_service_worker_registration_impl.h"
 #include "content/child/thread_safe_sender.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/push_messaging_messages.h"
 #include "third_party/WebKit/public/platform/WebString.h"
 #include "third_party/WebKit/public/platform/modules/push_messaging/WebPushSubscription.h"
@@ -21,7 +20,7 @@ namespace content {
 namespace {
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 // Returns the id of the given |service_worker_registration|, which
@@ -57,11 +56,11 @@ PushProvider* PushProvider::ThreadSpecificInstance(
   PushProvider* provider =
       new PushProvider(thread_safe_sender, push_dispatcher);
   if (CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(provider);
+    WorkerThread::AddObserver(provider);
   return provider;
 }
 
-void PushProvider::OnWorkerRunLoopStopped() {
+void PushProvider::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/push_messaging/push_provider.h b/content/child/push_messaging/push_provider.h
index 3826150..9a93dd2 100644
--- a/content/child/push_messaging/push_provider.h
+++ b/content/child/push_messaging/push_provider.h
@@ -12,7 +12,7 @@
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
 #include "content/child/push_messaging/push_dispatcher.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "content/public/common/push_messaging_status.h"
 #include "third_party/WebKit/public/platform/modules/push_messaging/WebPushError.h"
 #include "third_party/WebKit/public/platform/modules/push_messaging/WebPushProvider.h"
@@ -28,7 +28,7 @@ namespace content {
 class ThreadSafeSender;
 
 class PushProvider : public blink::WebPushProvider,
-                     public WorkerTaskRunner::Observer {
+                     public WorkerThread::Observer {
  public:
   ~PushProvider() override;
 
@@ -38,8 +38,8 @@ class PushProvider : public blink::WebPushProvider,
       ThreadSafeSender* thread_safe_sender,
       PushDispatcher* push_dispatcher);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   // blink::WebPushProvider implementation.
   virtual void subscribe(
diff --git a/content/child/quota_dispatcher.cc b/content/child/quota_dispatcher.cc
index fa766db..c63894a 100644
--- a/content/child/quota_dispatcher.cc
+++ b/content/child/quota_dispatcher.cc
@@ -53,7 +53,7 @@ class WebStorageQuotaDispatcherCallback : public QuotaDispatcher::Callback {
 };
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 }  // namespace
@@ -83,12 +83,12 @@ QuotaDispatcher* QuotaDispatcher::ThreadSpecificInstance(
 
   QuotaDispatcher* dispatcher = new QuotaDispatcher(
       thread_safe_sender, quota_message_filter);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
-void QuotaDispatcher::OnWorkerRunLoopStopped() {
+void QuotaDispatcher::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/quota_dispatcher.h b/content/child/quota_dispatcher.h
index f4111e6..a141290 100644
--- a/content/child/quota_dispatcher.h
+++ b/content/child/quota_dispatcher.h
@@ -11,7 +11,7 @@
 #include "base/basictypes.h"
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "storage/common/quota/quota_types.h"
 
 class GURL;
@@ -33,7 +33,7 @@ class QuotaMessageFilter;
 // process from/to the main browser process.  There is one instance
 // per each thread.  Thread-specific instance can be obtained by
 // ThreadSpecificInstance().
-class QuotaDispatcher : public WorkerTaskRunner::Observer {
+class QuotaDispatcher : public WorkerThread::Observer {
  public:
   class Callback {
    public:
@@ -53,8 +53,8 @@ class QuotaDispatcher : public WorkerTaskRunner::Observer {
       ThreadSafeSender* thread_safe_sender,
       QuotaMessageFilter* quota_message_filter);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   void OnMessageReceived(const IPC::Message& msg);
 
diff --git a/content/child/service_worker/service_worker_dispatcher.cc b/content/child/service_worker/service_worker_dispatcher.cc
index 03e9ee9..a3cf500 100644
--- a/content/child/service_worker/service_worker_dispatcher.cc
+++ b/content/child/service_worker/service_worker_dispatcher.cc
@@ -40,7 +40,7 @@ base::LazyInstance<ThreadLocalPointer<void>>::Leaky g_dispatcher_tls =
 void* const kHasBeenDeleted = reinterpret_cast<void*>(0x1);
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 }  // namespace
@@ -254,8 +254,8 @@ ServiceWorkerDispatcher::GetOrCreateThreadSpecificInstance(
 
   ServiceWorkerDispatcher* dispatcher =
       new ServiceWorkerDispatcher(thread_safe_sender, main_thread_task_runner);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
@@ -266,7 +266,7 @@ ServiceWorkerDispatcher* ServiceWorkerDispatcher::GetThreadSpecificInstance() {
       g_dispatcher_tls.Pointer()->Get());
 }
 
-void ServiceWorkerDispatcher::OnWorkerRunLoopStopped() {
+void ServiceWorkerDispatcher::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/child/service_worker/service_worker_dispatcher.h b/content/child/service_worker/service_worker_dispatcher.h
index c596ab4..2215156 100644
--- a/content/child/service_worker/service_worker_dispatcher.h
+++ b/content/child/service_worker/service_worker_dispatcher.h
@@ -11,7 +11,7 @@
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
 #include "base/strings/string16.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerError.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerProvider.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerRegistration.h"
@@ -48,8 +48,7 @@ struct ServiceWorkerVersionAttributes;
 // This class manages communication with the browser process about
 // registration of the service worker, exposed to renderer and worker
 // scripts through methods like navigator.registerServiceWorker().
-class CONTENT_EXPORT ServiceWorkerDispatcher
-    : public WorkerTaskRunner::Observer {
+class CONTENT_EXPORT ServiceWorkerDispatcher : public WorkerThread::Observer {
  public:
   typedef blink::WebServiceWorkerProvider::WebServiceWorkerRegistrationCallbacks
       WebServiceWorkerRegistrationCallbacks;
@@ -180,8 +179,8 @@ class CONTENT_EXPORT ServiceWorkerDispatcher
   friend class WebServiceWorkerImpl;
   friend class WebServiceWorkerRegistrationImpl;
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   void OnAssociateRegistrationWithServiceWorker(
       int thread_id,
diff --git a/content/child/worker_task_runner.cc b/content/child/worker_task_runner.cc
index bd469c1..875e102 100644
--- a/content/child/worker_task_runner.cc
+++ b/content/child/worker_task_runner.cc
@@ -13,6 +13,7 @@
 #include "base/single_thread_task_runner.h"
 #include "base/stl_util.h"
 #include "base/thread_task_runner_handle.h"
+#include "content/child/worker_thread_impl.h"
 
 namespace content {
 
@@ -37,11 +38,6 @@ class DoNothingTaskRunner : public base::TaskRunner {
 
 }  // namespace
 
-struct WorkerTaskRunner::ThreadLocalState {
-  ThreadLocalState() {}
-  base::ObserverList<WorkerTaskRunner::Observer> stop_observers_;
-};
-
 WorkerTaskRunner::WorkerTaskRunner()
     : task_runner_for_dead_worker_(new DoNothingTaskRunner()) {
 }
@@ -63,52 +59,33 @@ int WorkerTaskRunner::PostTaskToAllThreads(const base::Closure& closure) {
   return static_cast<int>(task_runner_map_.size());
 }
 
-int WorkerTaskRunner::CurrentWorkerId() {
-  if (!current_tls_.Get())
-    return 0;
-  return base::PlatformThread::CurrentId();
-}
-
 WorkerTaskRunner* WorkerTaskRunner::Instance() {
   static base::LazyInstance<WorkerTaskRunner>::Leaky
       worker_task_runner = LAZY_INSTANCE_INITIALIZER;
   return worker_task_runner.Pointer();
 }
 
-void WorkerTaskRunner::AddStopObserver(Observer* obs) {
-  DCHECK(CurrentWorkerId() > 0);
-  current_tls_.Get()->stop_observers_.AddObserver(obs);
-}
-
-void WorkerTaskRunner::RemoveStopObserver(Observer* obs) {
-  DCHECK(CurrentWorkerId() > 0);
-  current_tls_.Get()->stop_observers_.RemoveObserver(obs);
-}
-
 WorkerTaskRunner::~WorkerTaskRunner() {
 }
 
-void WorkerTaskRunner::OnWorkerRunLoopStarted() {
-  DCHECK(!current_tls_.Get());
+void WorkerTaskRunner::DidStartWorkerRunLoop() {
   DCHECK(!base::PlatformThread::CurrentRef().is_null());
-  current_tls_.Set(new ThreadLocalState());
-
+  // Note: call into WorkerThreadImpl rather than this class observing
+  // WorkerThreadImpl, to ensure that the task runner exists before anybody is
+  // notified that the worker thread has started.
+  WorkerThreadImpl::DidStartCurrentWorkerThread();
   int id = base::PlatformThread::CurrentId();
   base::AutoLock locker_(task_runner_map_lock_);
   task_runner_map_[id] = base::ThreadTaskRunnerHandle::Get().get();
   CHECK(task_runner_map_[id]);
 }
 
-void WorkerTaskRunner::OnWorkerRunLoopStopped() {
-  DCHECK(current_tls_.Get());
-  FOR_EACH_OBSERVER(Observer, current_tls_.Get()->stop_observers_,
-                    OnWorkerRunLoopStopped());
+void WorkerTaskRunner::WillStopWorkerRunLoop() {
+  WorkerThreadImpl::WillStopCurrentWorkerThread();
   {
     base::AutoLock locker(task_runner_map_lock_);
-    task_runner_map_.erase(CurrentWorkerId());
+    task_runner_map_.erase(WorkerThread::GetCurrentId());
   }
-  delete current_tls_.Get();
-  current_tls_.Set(NULL);
 }
 
 base::TaskRunner* WorkerTaskRunner::GetTaskRunnerFor(int worker_id) {
diff --git a/content/child/worker_task_runner.h b/content/child/worker_task_runner.h
index c3797bc..24ae41a 100644
--- a/content/child/worker_task_runner.h
+++ b/content/child/worker_task_runner.h
@@ -11,8 +11,8 @@
 #include "base/memory/ref_counted.h"
 #include "base/synchronization/lock.h"
 #include "base/threading/platform_thread.h"
-#include "base/threading/thread_local.h"
 #include "content/common/content_export.h"
+#include "content/public/child/worker_thread.h"
 
 namespace base {
 class TaskRunner;
@@ -26,22 +26,10 @@ class CONTENT_EXPORT WorkerTaskRunner {
 
   bool PostTask(int id, const base::Closure& task);
   int PostTaskToAllThreads(const base::Closure& task);
-  int CurrentWorkerId();
   static WorkerTaskRunner* Instance();
 
-  class CONTENT_EXPORT Observer {
-   public:
-    virtual ~Observer() {}
-    virtual void OnWorkerRunLoopStopped() = 0;
-  };
-  // Add/Remove an observer that will get notified when the current worker run
-  // loop is stopping. This observer will not get notified when other threads
-  // are stopping.  It's only valid to call these on a worker thread.
-  void AddStopObserver(Observer* observer);
-  void RemoveStopObserver(Observer* observer);
-
-  void OnWorkerRunLoopStarted();
-  void OnWorkerRunLoopStopped();
+  void DidStartWorkerRunLoop();
+  void WillStopWorkerRunLoop();
 
   base::TaskRunner* GetTaskRunnerFor(int worker_id);
 
@@ -60,9 +48,6 @@ class CONTENT_EXPORT WorkerTaskRunner {
   // which silently discards all the tasks it receives.
   scoped_refptr<base::TaskRunner> task_runner_for_dead_worker_;
 
-  struct ThreadLocalState;
-  base::ThreadLocalPointer<ThreadLocalState> current_tls_;
-
   IDToTaskRunnerMap task_runner_map_;
   base::Lock task_runner_map_lock_;
 };
diff --git a/content/child/worker_task_runner_unittest.cc b/content/child/worker_task_runner_unittest.cc
index 20eddfb..5e932b5 100644
--- a/content/child/worker_task_runner_unittest.cc
+++ b/content/child/worker_task_runner_unittest.cc
@@ -6,6 +6,7 @@
 
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
+#include "content/public/child/worker_thread.h"
 #include "testing/gmock/include/gmock/gmock.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -13,38 +14,32 @@ namespace content {
 
 class WorkerTaskRunnerTest : public testing::Test {
  public:
-  void FakeStart() {
-    task_runner_.OnWorkerRunLoopStarted();
-  }
-  void FakeStop() {
-    task_runner_.OnWorkerRunLoopStopped();
-  }
+  void FakeStart() { task_runner_.DidStartWorkerRunLoop(); }
+  void FakeStop() { task_runner_.WillStopWorkerRunLoop(); }
   WorkerTaskRunner task_runner_;
 
  private:
   base::MessageLoop message_loop_;
 };
 
-class MockObserver : public WorkerTaskRunner::Observer {
+class MockObserver : public WorkerThread::Observer {
  public:
-  MOCK_METHOD0(OnWorkerRunLoopStopped, void());
+  MOCK_METHOD0(WillStopCurrentWorkerThread, void());
   void RemoveSelfOnNotify() {
-    ON_CALL(*this, OnWorkerRunLoopStopped()).WillByDefault(
-        testing::Invoke(this, &MockObserver::RemoveSelf));
-  }
-  void RemoveSelf() {
-    runner_->RemoveStopObserver(this);
+    ON_CALL(*this, WillStopCurrentWorkerThread())
+        .WillByDefault(testing::Invoke(this, &MockObserver::RemoveSelf));
   }
+  void RemoveSelf() { WorkerThread::RemoveObserver(this); }
   WorkerTaskRunner* runner_;
 };
 
 TEST_F(WorkerTaskRunnerTest, BasicObservingAndWorkerId) {
-  ASSERT_EQ(0, task_runner_.CurrentWorkerId());
+  ASSERT_EQ(0, WorkerThread::GetCurrentId());
   MockObserver o;
-  EXPECT_CALL(o, OnWorkerRunLoopStopped()).Times(1);
+  EXPECT_CALL(o, WillStopCurrentWorkerThread()).Times(1);
   FakeStart();
-  task_runner_.AddStopObserver(&o);
-  ASSERT_LT(0, task_runner_.CurrentWorkerId());
+  WorkerThread::AddObserver(&o);
+  ASSERT_LT(0, WorkerThread::GetCurrentId());
   FakeStop();
 }
 
@@ -52,9 +47,9 @@ TEST_F(WorkerTaskRunnerTest, CanRemoveSelfDuringNotification) {
   MockObserver o;
   o.RemoveSelfOnNotify();
   o.runner_ = &task_runner_;
-  EXPECT_CALL(o, OnWorkerRunLoopStopped()).Times(1);
+  EXPECT_CALL(o, WillStopCurrentWorkerThread()).Times(1);
   FakeStart();
-  task_runner_.AddStopObserver(&o);
+  WorkerThread::AddObserver(&o);
   FakeStop();
 }
 
diff --git a/content/child/worker_thread_impl.cc b/content/child/worker_thread_impl.cc
index c499ccb..2f4549d 100644
--- a/content/child/worker_thread_impl.cc
+++ b/content/child/worker_thread_impl.cc
@@ -2,16 +2,37 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "content/public/child/worker_thread.h"
+#include "content/child/worker_thread_impl.h"
 
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/observer_list.h"
+#include "base/threading/thread_local.h"
 #include "content/child/worker_task_runner.h"
 #include "content/common/content_export.h"
+#include "content/public/child/worker_thread.h"
 
 namespace content {
 
+namespace {
+
+using WorkerThreadObservers = base::ObserverList<WorkerThread::Observer>;
+using ThreadLocalWorkerThreadObservers =
+    base::ThreadLocalPointer<WorkerThreadObservers>;
+
+// Stores a WorkerThreadObservers instance per thread.
+base::LazyInstance<ThreadLocalWorkerThreadObservers> g_observers_tls =
+    LAZY_INSTANCE_INITIALIZER;
+
+}  // namespace
+
+// WorkerThread:
+
 // static
 int WorkerThread::GetCurrentId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  if (!g_observers_tls.Get().Get())
+    return 0;
+  return base::PlatformThread::CurrentId();
 }
 
 // static
@@ -19,4 +40,40 @@ void WorkerThread::PostTask(int id, const base::Closure& task) {
   WorkerTaskRunner::Instance()->PostTask(id, task);
 }
 
+// static
+void WorkerThread::AddObserver(Observer* observer) {
+  DCHECK(GetCurrentId() > 0);
+  WorkerThreadObservers* observers = g_observers_tls.Get().Get();
+  DCHECK(observers);
+  observers->AddObserver(observer);
+}
+
+// static
+void WorkerThread::RemoveObserver(Observer* observer) {
+  DCHECK(GetCurrentId() > 0);
+  WorkerThreadObservers* observers = g_observers_tls.Get().Get();
+  DCHECK(observers);
+  observers->RemoveObserver(observer);
+}
+
+// WorkerThreadImpl:
+
+// static
+void WorkerThreadImpl::DidStartCurrentWorkerThread() {
+  ThreadLocalWorkerThreadObservers& observers_tls = g_observers_tls.Get();
+  DCHECK(!observers_tls.Get());
+  observers_tls.Set(new WorkerThreadObservers());
+}
+
+// static
+void WorkerThreadImpl::WillStopCurrentWorkerThread() {
+  ThreadLocalWorkerThreadObservers& observers_tls = g_observers_tls.Get();
+  WorkerThreadObservers* observers = observers_tls.Get();
+  DCHECK(observers);
+  FOR_EACH_OBSERVER(WorkerThread::Observer, *observers,
+                    WillStopCurrentWorkerThread());
+  delete observers;
+  observers_tls.Set(nullptr);
+}
+
 }  // namespace content
diff --git a/content/child/worker_thread_impl.h b/content/child/worker_thread_impl.h
new file mode 100644
index 0000000..55cc153
--- /dev/null
+++ b/content/child/worker_thread_impl.h
@@ -0,0 +1,19 @@
+// 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.
+
+#include "base/macros.h"
+
+namespace content {
+
+// WorkerThread-related methods only exposed within the content module.
+class WorkerThreadImpl {
+ public:
+  static void DidStartCurrentWorkerThread();
+  static void WillStopCurrentWorkerThread();
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(WorkerThreadImpl);
+};
+
+}  // namespace content
diff --git a/content/child/worker_thread_message_filter.cc b/content/child/worker_thread_message_filter.cc
index aa11b3b..77770ab 100644
--- a/content/child/worker_thread_message_filter.cc
+++ b/content/child/worker_thread_message_filter.cc
@@ -38,7 +38,7 @@ bool WorkerThreadMessageFilter::OnMessageReceived(const IPC::Message& msg) {
   // If the IPC message is received in a worker thread, but it has already been
   // stopped, then drop the message.
   if (!main_thread_task_runner_->BelongsToCurrentThread() &&
-      !WorkerTaskRunner::Instance()->CurrentWorkerId()) {
+      !WorkerThread::GetCurrentId()) {
     return false;
   }
   OnFilteredMessageReceived(msg);
diff --git a/content/content_child.gypi b/content/content_child.gypi
index f08dd47..5ad5b67 100644
--- a/content/content_child.gypi
+++ b/content/content_child.gypi
@@ -284,6 +284,7 @@
       'child/worker_task_runner.cc',
       'child/worker_task_runner.h',
       'child/worker_thread_impl.cc',
+      'child/worker_thread_impl.h',
       'child/worker_thread_message_filter.cc',
       'child/worker_thread_message_filter.h',
     ],
diff --git a/content/public/child/worker_thread.h b/content/public/child/worker_thread.h
index e8ed64c..983f09a 100644
--- a/content/public/child/worker_thread.h
+++ b/content/public/child/worker_thread.h
@@ -17,6 +17,25 @@ namespace content {
 // posting tasks back to them.
 class CONTENT_EXPORT WorkerThread {
  public:
+  // Observes worker thread lifetime.
+  class CONTENT_EXPORT Observer {
+   public:
+    virtual ~Observer() {}
+
+    // Notifies the observer that the current worker thread is about to be
+    // stopped.
+    //
+    // The worker state may have already been destroyed. To observe that, use
+    // ContentRendererClient::WillDestroyServiceWorkerContextOnWorkerThread.
+    virtual void WillStopCurrentWorkerThread() {}
+  };
+
+  // Adds/removes an Observer. Observers are stored per-thread, so it is only
+  // valid to call these from a worker thread, and events will be dispatched on
+  // that worker's thread.
+  static void AddObserver(Observer* observer);
+  static void RemoveObserver(Observer* observer);
+
   // Returns the thread ID for the current worker thread, or 0 if this is not a
   // worker thread (for example, the render thread). Worker thread IDs will
   // always be > 0.
diff --git a/content/renderer/bluetooth/bluetooth_dispatcher.cc b/content/renderer/bluetooth/bluetooth_dispatcher.cc
index 1a38354..1a4679e 100644
--- a/content/renderer/bluetooth/bluetooth_dispatcher.cc
+++ b/content/renderer/bluetooth/bluetooth_dispatcher.cc
@@ -72,7 +72,7 @@ base::LazyInstance<base::ThreadLocalPointer<void>>::Leaky g_dispatcher_tls =
 void* const kHasBeenDeleted = reinterpret_cast<void*>(0x1);
 
 int CurrentWorkerId() {
-  return WorkerTaskRunner::Instance()->CurrentWorkerId();
+  return WorkerThread::GetCurrentId();
 }
 
 WebBluetoothDevice::VendorIDSource GetWebVendorIdSource(
@@ -111,7 +111,7 @@ BluetoothDispatcher* BluetoothDispatcher::GetOrCreateThreadSpecificInstance(
 
   BluetoothDispatcher* dispatcher = new BluetoothDispatcher(thread_safe_sender);
   if (CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
@@ -225,7 +225,7 @@ void BluetoothDispatcher::writeValue(
       CurrentWorkerId(), request_id, characteristic_instance_id.utf8(), value));
 }
 
-void BluetoothDispatcher::OnWorkerRunLoopStopped() {
+void BluetoothDispatcher::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/renderer/bluetooth/bluetooth_dispatcher.h b/content/renderer/bluetooth/bluetooth_dispatcher.h
index 1a704a7..4109414 100644
--- a/content/renderer/bluetooth/bluetooth_dispatcher.h
+++ b/content/renderer/bluetooth/bluetooth_dispatcher.h
@@ -7,8 +7,8 @@
 
 #include "base/id_map.h"
 #include "base/memory/ref_counted.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/bluetooth/bluetooth_device.h"
+#include "content/public/child/worker_thread.h"
 #include "third_party/WebKit/public/platform/modules/bluetooth/WebBluetooth.h"
 #include "third_party/WebKit/public/platform/modules/bluetooth/WebBluetoothError.h"
 
@@ -35,7 +35,7 @@ class ThreadSafeSender;
 // Incoming IPC messages are received by the BluetoothMessageFilter and
 // directed to the thread specific instance of this class.
 // Outgoing messages come from WebBluetoothImpl.
-class BluetoothDispatcher : public WorkerTaskRunner::Observer {
+class BluetoothDispatcher : public WorkerThread::Observer {
  public:
   explicit BluetoothDispatcher(ThreadSafeSender* sender);
   ~BluetoothDispatcher() override;
@@ -70,8 +70,8 @@ class BluetoothDispatcher : public WorkerTaskRunner::Observer {
                   const std::vector<uint8_t>& value,
                   blink::WebBluetoothWriteValueCallbacks*);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
  private:
   // IPC Handlers, see definitions in bluetooth_messages.h.
diff --git a/content/renderer/cache_storage/cache_storage_dispatcher.cc b/content/renderer/cache_storage/cache_storage_dispatcher.cc
index 95b10e3..c2612ef 100644
--- a/content/renderer/cache_storage/cache_storage_dispatcher.cc
+++ b/content/renderer/cache_storage/cache_storage_dispatcher.cc
@@ -220,12 +220,12 @@ CacheStorageDispatcher* CacheStorageDispatcher::ThreadSpecificInstance(
 
   CacheStorageDispatcher* dispatcher =
       new CacheStorageDispatcher(thread_safe_sender);
-  if (WorkerTaskRunner::Instance()->CurrentWorkerId())
-    WorkerTaskRunner::Instance()->AddStopObserver(dispatcher);
+  if (WorkerThread::GetCurrentId())
+    WorkerThread::AddObserver(dispatcher);
   return dispatcher;
 }
 
-void CacheStorageDispatcher::OnWorkerRunLoopStopped() {
+void CacheStorageDispatcher::WillStopCurrentWorkerThread() {
   delete this;
 }
 
diff --git a/content/renderer/cache_storage/cache_storage_dispatcher.h b/content/renderer/cache_storage/cache_storage_dispatcher.h
index 8e31b0b..f08712c 100644
--- a/content/renderer/cache_storage/cache_storage_dispatcher.h
+++ b/content/renderer/cache_storage/cache_storage_dispatcher.h
@@ -12,7 +12,7 @@
 #include "base/memory/weak_ptr.h"
 #include "base/strings/string16.h"
 #include "base/time/time.h"
-#include "content/child/worker_task_runner.h"
+#include "content/public/child/worker_thread.h"
 #include "content/public/renderer/render_process_observer.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerCache.h"
 #include "third_party/WebKit/public/platform/modules/serviceworker/WebServiceWorkerCacheError.h"
@@ -26,7 +26,7 @@ struct ServiceWorkerResponse;
 
 // Handle the Cache Storage messaging for this context thread. The
 // main thread and each worker thread have their own instances.
-class CacheStorageDispatcher : public WorkerTaskRunner::Observer {
+class CacheStorageDispatcher : public WorkerThread::Observer {
  public:
   explicit CacheStorageDispatcher(ThreadSafeSender* thread_safe_sender);
   ~CacheStorageDispatcher() override;
@@ -36,8 +36,8 @@ class CacheStorageDispatcher : public WorkerTaskRunner::Observer {
   static CacheStorageDispatcher* ThreadSpecificInstance(
       ThreadSafeSender* thread_safe_sender);
 
-  // WorkerTaskRunner::Observer implementation.
-  void OnWorkerRunLoopStopped() override;
+  // WorkerThread::Observer implementation.
+  void WillStopCurrentWorkerThread() override;
 
   bool Send(IPC::Message* msg);
 
@@ -173,9 +173,7 @@ class CacheStorageDispatcher : public WorkerTaskRunner::Observer {
   using BatchCallbacksMap =
       IDMap<blink::WebServiceWorkerCache::CacheBatchCallbacks, IDMapOwnPointer>;
 
-  static int32 CurrentWorkerId() {
-    return WorkerTaskRunner::Instance()->CurrentWorkerId();
-  }
+  static int32 CurrentWorkerId() { return WorkerThread::GetCurrentId(); }
 
   void PopulateWebResponseFromResponse(
       const ServiceWorkerResponse& response,
diff --git a/content/renderer/service_worker/service_worker_context_client.cc b/content/renderer/service_worker/service_worker_context_client.cc
index de57d4c..d3af28f 100644
--- a/content/renderer/service_worker/service_worker_context_client.cc
+++ b/content/renderer/service_worker/service_worker_context_client.cc
@@ -24,7 +24,6 @@
 #include "content/child/service_worker/web_service_worker_registration_impl.h"
 #include "content/child/thread_safe_sender.h"
 #include "content/child/webmessageportchannel_impl.h"
-#include "content/child/worker_task_runner.h"
 #include "content/common/devtools_messages.h"
 #include "content/common/message_port_messages.h"
 #include "content/common/mojo/service_registry_impl.h"
@@ -339,7 +338,7 @@ void ServiceWorkerContextClient::workerContextFailedToStart() {
 void ServiceWorkerContextClient::workerContextStarted(
     blink::WebServiceWorkerContextProxy* proxy) {
   DCHECK(!worker_task_runner_.get());
-  DCHECK_NE(0, WorkerTaskRunner::Instance()->CurrentWorkerId());
+  DCHECK_NE(0, WorkerThread::GetCurrentId());
   worker_task_runner_ = base::ThreadTaskRunnerHandle::Get();
   // g_worker_client_tls.Pointer()->Get() could return NULL if this context
   // gets deleted before workerContextStarted() is called.
@@ -363,8 +362,7 @@ void ServiceWorkerContextClient::workerContextStarted(
   SetRegistrationInServiceWorkerGlobalScope();
 
   Send(new EmbeddedWorkerHostMsg_WorkerScriptLoaded(
-      embedded_worker_id_,
-      WorkerTaskRunner::Instance()->CurrentWorkerId(),
+      embedded_worker_id_, WorkerThread::GetCurrentId(),
       provider_context_->provider_id()));
 
   TRACE_EVENT_ASYNC_STEP_INTO0(
@@ -389,16 +387,17 @@ void ServiceWorkerContextClient::didEvaluateWorkerScript(bool success) {
 void ServiceWorkerContextClient::didInitializeWorkerContext(
     v8::Local<v8::Context> context,
     const blink::WebURL& url) {
-  // TODO(annekao): Remove WebURL parameter from Blink (since url and script_url
-  // are equal). Also remove m_documentURL from ServiceWorkerGlobalScopeProxy.
-  DCHECK_EQ(script_url_, GURL(url));
+  // TODO(annekao): Remove WebURL parameter from Blink, it's at best redundant
+  // given |script_url_|, and may be empty in the future.
+  // Also remove m_documentURL from ServiceWorkerGlobalScopeProxy.
   GetContentClient()
       ->renderer()
       ->DidInitializeServiceWorkerContextOnWorkerThread(context, script_url_);
 }
 
-void ServiceWorkerContextClient::willDestroyWorkerContext() {
-  // At this point OnWorkerRunLoopStopped is already called, so
+void ServiceWorkerContextClient::willDestroyWorkerContext(
+    v8::Local<v8::Context> context) {
+  // At this point WillStopCurrentWorkerThread is already called, so
   // worker_task_runner_->RunsTasksOnCurrentThread() returns false
   // (while we're still on the worker thread).
   proxy_ = NULL;
diff --git a/content/renderer/service_worker/service_worker_context_client.h b/content/renderer/service_worker/service_worker_context_client.h
index 54fd780b..339d3b0 100644
--- a/content/renderer/service_worker/service_worker_context_client.h
+++ b/content/renderer/service_worker/service_worker_context_client.h
@@ -103,7 +103,7 @@ class ServiceWorkerContextClient
   virtual void didEvaluateWorkerScript(bool success);
   virtual void didInitializeWorkerContext(v8::Local<v8::Context> context,
                                           const blink::WebURL& url);
-  virtual void willDestroyWorkerContext();
+  virtual void willDestroyWorkerContext(v8::Local<v8::Context> context);
   virtual void workerContextDestroyed();
   virtual void reportException(const blink::WebString& error_message,
                                int line_number,