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..ea0c0eb484c37b006ad574e3ddaf76d759ddb7b5 100644
--- a/content/common/input_messages.h
+++ b/content/common/input_messages.h
@@ -260,6 +260,11 @@ IPC_MESSAGE_ROUTED0(InputMsg_ImeEventAck)
 
 // Request from browser to update text input state.
 IPC_MESSAGE_ROUTED0(InputMsg_RequestTextInputStateUpdate)
+
+// Request from browser to update the cursor and composition information.
+IPC_MESSAGE_ROUTED2(InputMsg_RequestCursorUpdate,
+                    bool /* immediate request */,
+                    bool /* monitor request */)
 #endif
 
 IPC_MESSAGE_ROUTED0(InputMsg_SyntheticGestureCompleted)