Send input event IPCs directly from the UI thread

ipc/mojo/ipc_channel_mojo.cc

Index: ipc/mojo/ipc_channel_mojo.cc
diff --git a/ipc/mojo/ipc_channel_mojo.cc b/ipc/mojo/ipc_channel_mojo.cc
index a46ccde21d9a88149a82a9d297ad3fe914073bf3..47634204bf62628e0464783dfe47602e3fb0f45b 100644
--- a/ipc/mojo/ipc_channel_mojo.cc
+++ b/ipc/mojo/ipc_channel_mojo.cc
@@ -346,7 +346,7 @@ bool ChannelMojo::Send(Message* message) {
 }
 
 bool ChannelMojo::IsSendThreadSafe() const {
-  return false;
+  return true;

[piman, 2016/05/24 17:24:51]

I also noted that SyncMessageFilter will also skip the IO thread hops if this is
true - causing equivalent issues in at least GPU code. Could it be fixed
similarly to ChannelProxy in this CL, before turning this on?

[Ken Rockot(use gerrit already), 2016/05/24 18:00:08]

Thanks, forgot about SyncMessageFilter. So for now I've also added SendNow to
SyncMessageFilter but haven't added any consumers. Send always posts.

 }
 
 base::ProcessId ChannelMojo::GetPeerPID() const {