ipc: Make factory methods for attachment brokers.

This is a refactor with no intended functional effects.

BUG=535711

Review URL: https://codereview.chromium.org/1382303003

Cr-Commit-Position: refs/heads/master@{#352735}

6 files changed, 63 insertions, 8 deletions

diff --git a/ipc/attachment_broker.cc b/ipc/attachment_broker.cc
index 2fc4fb4..dac046b 100644
--- a/ipc/attachment_broker.cc
+++ b/ipc/attachment_broker.cc
@@ -14,8 +14,9 @@ namespace IPC {
 
 // static
 void AttachmentBroker::SetGlobal(AttachmentBroker* broker) {
-  CHECK(!g_attachment_broker)
-      << "An attachment broker already exists with memory address: " << broker;
+  CHECK(!g_attachment_broker || !broker)
+      << "Global attachment broker address: " << broker
+      << ". New attachment broker address: " << broker;
   g_attachment_broker = broker;
 }
 
diff --git a/ipc/attachment_broker_privileged.cc b/ipc/attachment_broker_privileged.cc
index 0f3ac48..d040392 100644
--- a/ipc/attachment_broker_privileged.cc
+++ b/ipc/attachment_broker_privileged.cc
@@ -9,11 +9,30 @@
 #include "base/metrics/histogram_macros.h"
 #include "ipc/ipc_endpoint.h"
 
+#if defined(OS_WIN)
+#include "ipc/attachment_broker_privileged_win.h"
+#endif
+
 namespace IPC {
 
-AttachmentBrokerPrivileged::AttachmentBrokerPrivileged() {}
+AttachmentBrokerPrivileged::AttachmentBrokerPrivileged() {
+  IPC::AttachmentBroker::SetGlobal(this);
+}
 
-AttachmentBrokerPrivileged::~AttachmentBrokerPrivileged() {}
+AttachmentBrokerPrivileged::~AttachmentBrokerPrivileged() {
+  IPC::AttachmentBroker::SetGlobal(nullptr);
+}
+
+// static
+scoped_ptr<AttachmentBrokerPrivileged>
+AttachmentBrokerPrivileged::CreateBroker() {
+#if defined(OS_WIN)
+  return scoped_ptr<AttachmentBrokerPrivileged>(
+      new IPC::AttachmentBrokerPrivilegedWin);
+#else
+  return nullptr;
+#endif
+}
 
 void AttachmentBrokerPrivileged::RegisterCommunicationChannel(
     Endpoint* endpoint) {
diff --git a/ipc/attachment_broker_privileged.h b/ipc/attachment_broker_privileged.h
index 7b3975a..0d5f4a8 100644
--- a/ipc/attachment_broker_privileged.h
+++ b/ipc/attachment_broker_privileged.h
@@ -7,6 +7,7 @@
 
 #include <vector>
 
+#include "base/memory/scoped_ptr.h"
 #include "ipc/attachment_broker.h"
 #include "ipc/ipc_export.h"
 
@@ -24,6 +25,14 @@ class IPC_EXPORT AttachmentBrokerPrivileged : public IPC::AttachmentBroker {
   AttachmentBrokerPrivileged();
   ~AttachmentBrokerPrivileged() override;
 
+   // On platforms that support attachment brokering, returns a new instance of
+   // a platform-specific attachment broker. Otherwise returns |nullptr|.
+   // The caller takes ownership of the newly created instance, and is
+   // responsible for ensuring that the attachment broker lives longer than
+   // every IPC::Channel. The new instance automatically registers itself as the
+   // global attachment broker.
+  static scoped_ptr<AttachmentBrokerPrivileged> CreateBroker();
+
   // Each unprivileged process should have one IPC channel on which it
   // communicates attachment information with the broker process. In the broker
   // process, these channels must be registered and deregistered with the
diff --git a/ipc/attachment_broker_privileged_win_unittest.cc b/ipc/attachment_broker_privileged_win_unittest.cc
index 9c4a1195..25cadcb 100644
--- a/ipc/attachment_broker_privileged_win_unittest.cc
+++ b/ipc/attachment_broker_privileged_win_unittest.cc
@@ -220,7 +220,6 @@ class IPCAttachmentBrokerPrivilegedWinTest : public IPCTestBase {
   // Takes ownership of |broker|. Has no effect if called after CommonSetUp().
   void set_broker(IPC::AttachmentBrokerUnprivilegedWin* broker) {
     broker_.reset(broker);
-    IPC::AttachmentBroker::SetGlobal(broker);
   }
 
   void CommonSetUp() {
@@ -427,7 +426,6 @@ int CommonPrivilegedProcessMain(OnMessageReceivedCallback callback,
 
   // Set up IPC channel.
   IPC::AttachmentBrokerPrivilegedWin broker;
-  IPC::AttachmentBroker::SetGlobal(&broker);
   scoped_ptr<IPC::Channel> channel(IPC::Channel::CreateClient(
       IPCTestBase::GetChannelName(channel_name), &listener));
   broker.RegisterCommunicationChannel(channel.get());
diff --git a/ipc/attachment_broker_unprivileged.cc b/ipc/attachment_broker_unprivileged.cc
index ce4e8ab..75f61e4 100644
--- a/ipc/attachment_broker_unprivileged.cc
+++ b/ipc/attachment_broker_unprivileged.cc
@@ -8,12 +8,31 @@
 #include "ipc/ipc_channel.h"
 #include "ipc/ipc_endpoint.h"
 
+#if defined(OS_WIN)
+#include "ipc/attachment_broker_unprivileged_win.h"
+#endif
+
 namespace IPC {
 
 AttachmentBrokerUnprivileged::AttachmentBrokerUnprivileged()
-    : sender_(nullptr) {}
+    : sender_(nullptr) {
+  IPC::AttachmentBroker::SetGlobal(this);
+}
 
-AttachmentBrokerUnprivileged::~AttachmentBrokerUnprivileged() {}
+AttachmentBrokerUnprivileged::~AttachmentBrokerUnprivileged() {
+  IPC::AttachmentBroker::SetGlobal(nullptr);
+}
+
+// static
+scoped_ptr<AttachmentBrokerUnprivileged>
+AttachmentBrokerUnprivileged::CreateBroker() {
+#if defined(OS_WIN)
+  return scoped_ptr<AttachmentBrokerUnprivileged>(
+      new IPC::AttachmentBrokerUnprivilegedWin);
+#else
+  return nullptr;
+#endif
+}
 
 void AttachmentBrokerUnprivileged::DesignateBrokerCommunicationChannel(
     Endpoint* endpoint) {
diff --git a/ipc/attachment_broker_unprivileged.h b/ipc/attachment_broker_unprivileged.h
index 4f847a6..26cc1bf 100644
--- a/ipc/attachment_broker_unprivileged.h
+++ b/ipc/attachment_broker_unprivileged.h
@@ -5,6 +5,7 @@
 #ifndef IPC_ATTACHMENT_BROKER_UNPRIVILEGED_H_
 #define IPC_ATTACHMENT_BROKER_UNPRIVILEGED_H_
 
+#include "base/memory/scoped_ptr.h"
 #include "ipc/attachment_broker.h"
 #include "ipc/ipc_export.h"
 
@@ -20,6 +21,14 @@ class IPC_EXPORT AttachmentBrokerUnprivileged : public IPC::AttachmentBroker {
   AttachmentBrokerUnprivileged();
   ~AttachmentBrokerUnprivileged() override;
 
+   // On platforms that support attachment brokering, returns a new instance of
+   // a platform-specific attachment broker. Otherwise returns |nullptr|.
+   // The caller takes ownership of the newly created instance, and is
+   // responsible for ensuring that the attachment broker lives longer than
+   // every IPC::Channel. The new instance automatically registers itself as the
+   // global attachment broker.
+  static scoped_ptr<AttachmentBrokerUnprivileged> CreateBroker();
+
   // In each unprivileged process, exactly one channel should be used to
   // communicate brokerable attachments with the broker process.
   void DesignateBrokerCommunicationChannel(Endpoint* endpoint);