Send input event IPCs directly from the UI thread

ipc/ipc_sync_message_filter.h

Index: ipc/ipc_sync_message_filter.h
diff --git a/ipc/ipc_sync_message_filter.h b/ipc/ipc_sync_message_filter.h
index 27584359ece7918f11bc62556201f2813ad70b15..d2ffe87922c8881687d4b120b1821bed08cd2c66 100644
--- a/ipc/ipc_sync_message_filter.h
+++ b/ipc/ipc_sync_message_filter.h
@@ -5,6 +5,7 @@
 #ifndef IPC_IPC_SYNC_MESSAGE_FILTER_H_
 #define IPC_IPC_SYNC_MESSAGE_FILTER_H_
 
+#include <memory>
 #include <set>
 
 #include "base/macros.h"
@@ -39,6 +40,10 @@ class IPC_EXPORT SyncMessageFilter : public MessageFilter, public Sender {
   void OnChannelClosing() override;
   bool OnMessageReceived(const Message& message) override;
 
+  // Like Send but may send immediately (instead of posting to the IPC thread)
+  // if the underlying Channel implements a thread-safe Send.
+  bool SendNow(std::unique_ptr<Message> message);
+
  protected:
   SyncMessageFilter(base::WaitableEvent* shutdown_event,
                     bool is_channel_send_thread_safe);