Do not calculate composition bounds until IME requests.

content/common/input_messages.h

Index: content/common/input_messages.h
diff --git a/content/common/input_messages.h b/content/common/input_messages.h
index 4d3c0ce4a639194a2f7c73680aff2ec049febb5e..5ca7f71e40ed7dd0a82e20208807abea47f0871a 100644
--- a/content/common/input_messages.h
+++ b/content/common/input_messages.h
@@ -262,6 +262,11 @@ IPC_MESSAGE_ROUTED0(InputMsg_ImeEventAck)
 IPC_MESSAGE_ROUTED0(InputMsg_RequestTextInputStateUpdate)
 #endif
 
+// Request from browser to update the cursor and composition information.
+IPC_MESSAGE_ROUTED2(InputMsg_RequestCompositionUpdate,
+                    bool /* immediate request */,
+                    bool /* monitor request */)
+
 IPC_MESSAGE_ROUTED0(InputMsg_SyntheticGestureCompleted)
 
 // -----------------------------------------------------------------------------