Do not calculate composition bounds until IME requests.

content/common/input_messages.h

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // IPC messages for input events and other messages that require processing in
 // order relative to input events.
 // Multiply-included message file, hence no include guard.
 
 #include "base/strings/string16.h"
 #include "build/build_config.h"
@@ skipping 242 matching lines @@
                     gfx::Point /* location */)
 
 #if defined(OS_ANDROID)
 // Sent by the browser as ACK to ViewHostMsg_TextInputState when necessary.
 // NOTE: ImeEventAck and other Ime* messages should be of the same type,
 // otherwise a race condition can happen.
 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_ROUTED1(InputMsg_RequestCursorUpdate, int /* mode */)
 #endif
 
 IPC_MESSAGE_ROUTED0(InputMsg_SyntheticGestureCompleted)
 
 // -----------------------------------------------------------------------------
 // Messages sent from the renderer to the browser.
 
 // Acknowledges receipt of a InputMsg_HandleInputEvent message.
 IPC_MESSAGE_ROUTED1(InputHostMsg_HandleInputEvent_ACK,
                     content::InputEventAck /* ack */)
@@ skipping 28 matching lines @@
 // This IPC message sends the character bounds after every composition change
 // to always have correct bound info.
 IPC_MESSAGE_ROUTED2(InputHostMsg_ImeCompositionRangeChanged,
                     gfx::Range /* composition range */,
                     std::vector<gfx::Rect> /* character bounds */)
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent InputMsg, then ifdefs for platform specific InputMsg, then
 // platform independent InputHostMsg, then ifdefs for platform specific
 // InputHostMsg.