Send input event IPCs directly from the UI thread

content/public/browser/render_process_host.h

Index: content/public/browser/render_process_host.h
diff --git a/content/public/browser/render_process_host.h b/content/public/browser/render_process_host.h
index 67fc03f27d938f4bbd0bac27ec35de5edd206aa0..198e7e53f4b450bf5a1c3d918e04f3f87d930845 100644
--- a/content/public/browser/render_process_host.h
+++ b/content/public/browser/render_process_host.h
@@ -178,6 +178,14 @@ class CONTENT_EXPORT RenderProcessHost : public IPC::Sender,
   // Returns the renderer channel.
   virtual IPC::ChannelProxy* GetChannel() = 0;
 
+  // Returns an IPC::Sender which tries to send messages immediately from the
+  // calling thread. The returned Sender is owned by the RenderProcessHost.
+  virtual IPC::Sender* GetImmediateSender() = 0;
+
+  // Returns an IPC::Sender which always sends messages from the IO thread's
+  // task queue. The returned Sender is owned by the RenderProcessHost.
+  virtual IPC::Sender* GetIOThreadSender() = 0;

[Charlie Reis, 2016/05/23 23:33:12]

These don't seem to have any callers outside content/ yet.  Is it possible to
add one for at least one of them?  (We generally don't add new public methods
until they're used by an embedder.)

https://www.chromium.org/developers/content-module/content-api
"only expose methods in the public API that embedders need. If a method is only
used by other code in content, it belongs in foo_impl.h and not foo.h."

+
   // Adds a message filter to the IPC channel.
   virtual void AddFilter(BrowserMessageFilter* filter) = 0;