Introduce ThreadedInputConnection behind a switch

content/renderer/render_widget.h

Index: content/renderer/render_widget.h
diff --git a/content/renderer/render_widget.h b/content/renderer/render_widget.h
index 9197d973c8981f9aa6947258816144731e53a40b..bc7818aa3fdf05824ff69723aebc7b4c48338cce 100644
--- a/content/renderer/render_widget.h
+++ b/content/renderer/render_widget.h
@@ -306,6 +306,7 @@ class CONTENT_EXPORT RenderWidget
   void QueueMessage(IPC::Message* msg, MessageDeliveryPolicy policy);
 
   // Handle start and finish of IME event guard.
+  bool IsFromImeDefault();
   void OnImeEventGuardStart(ImeEventGuard* guard);
   void OnImeEventGuardFinish(ImeEventGuard* guard);
 
@@ -462,6 +463,9 @@ class CONTENT_EXPORT RenderWidget
 
   // Called by the browser process for every required IME acknowledgement.
   void OnImeEventAck();
+
+  // Called by the browser process to update text input state.
+  void OnRequestTextInputStateUpdate();
 #endif
 
   // Notify the compositor about a change in viewport size. This should be