Send input event IPCs directly from the UI thread

content/browser/renderer_host/render_process_host_impl.h

Index: content/browser/renderer_host/render_process_host_impl.h
diff --git a/content/browser/renderer_host/render_process_host_impl.h b/content/browser/renderer_host/render_process_host_impl.h
index e46e2c511257b92098a5282633d58b3f1f738b0e..efb808ae1468c47a8ec44675384f2e32f5220590 100644
--- a/content/browser/renderer_host/render_process_host_impl.h
+++ b/content/browser/renderer_host/render_process_host_impl.h
@@ -135,6 +135,8 @@ class CONTENT_EXPORT RenderProcessHostImpl
   void SetSuddenTerminationAllowed(bool enabled) override;
   bool SuddenTerminationAllowed() const override;
   IPC::ChannelProxy* GetChannel() override;
+  IPC::Sender* GetImmediateSender() override;
+  IPC::Sender* GetIOThreadSender() override;
   void AddFilter(BrowserMessageFilter* filter) override;
   bool FastShutdownForPageCount(size_t count) override;
   bool FastShutdownStarted() const override;
@@ -291,8 +293,11 @@ class CONTENT_EXPORT RenderProcessHostImpl
   int32_t pending_views_;
 
  private:
-  friend class VisitRelayingRenderProcessHost;
+  class SafeSenderProxy;
+
   friend class ChildProcessLauncherBrowserTest_ChildSpawnFail_Test;
+  friend class SafeSenderProxy;
+  friend class VisitRelayingRenderProcessHost;
 
   std::unique_ptr<IPC::ChannelProxy> CreateChannelProxy(
       const std::string& channel_id);
@@ -300,6 +305,9 @@ class CONTENT_EXPORT RenderProcessHostImpl
   // Creates and adds the IO thread message filters.
   void CreateMessageFilters();
 
+  // Shared implementation for IPC::Senders exposed by this RPH.
+  bool SendImpl(std::unique_ptr<IPC::Message> message, bool send_now);
+
   // Registers Mojo services to be exposed to the renderer.
   void RegisterMojoServices();
 
@@ -362,6 +370,11 @@ class CONTENT_EXPORT RenderProcessHostImpl
   base::FilePath GetEventLogFilePathWithExtensions(const base::FilePath& file);
 #endif
 
+  // IPC::Senders which live as long as this RPH and provide safe, opaque
+  // access to ChannelProxy SendNow() and SendOnIOThread() respectively.
+  const std::unique_ptr<SafeSenderProxy> immediate_sender_;
+  const std::unique_ptr<SafeSenderProxy> io_thread_sender_;
+
   std::unique_ptr<MojoChildConnection> mojo_child_connection_;
   std::unique_ptr<MojoApplicationHost> mojo_application_host_;
 
@@ -407,7 +420,7 @@ class CONTENT_EXPORT RenderProcessHostImpl
   // instead of in the channel so that we ensure they're sent after init related
   // messages that are sent once the process handle is available.  This is
   // because the queued messages may have dependencies on the init messages.
-  std::queue<IPC::Message*> queued_messages_;
+  std::queue<std::unique_ptr<IPC::Message>> queued_messages_;
 
   // The globally-unique identifier for this RPH.
   const int id_;