[DevTools] Force page redraw when enabling screencast.

content/common/view_messages.h

 // Copyright (c) 2012 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 page rendering.
 // Multiply-included message file, hence no include guard.
 
 #include "base/memory/shared_memory.h"
 #include "base/process/process.h"
 #include "base/strings/string16.h"
@@ skipping 959 matching lines @@
 
 // Sent by browser to tell renderer compositor that some resources that were
 // given to the browser in a swap are not being used anymore.
 IPC_MESSAGE_ROUTED2(ViewMsg_ReclaimCompositorResources,
                     uint32 /* output_surface_id */,
                     cc::CompositorFrameAck /* ack */)
 
 IPC_MESSAGE_ROUTED0(ViewMsg_SelectWordAroundCaret)
 
 // Sent by the browser to ask the renderer to redraw.
+// If |request_id| is not zero, it is added to the forced frame's latency info
+// as ui::WINDOW_SNAPSHOT_FRAME_NUMBER_COMPONENT.
 IPC_MESSAGE_ROUTED1(ViewMsg_ForceRedraw,
                     int /* request_id */)
 
 // -----------------------------------------------------------------------------
 // Messages sent from the renderer to the browser.
 
 // Sent by the renderer when it is creating a new window.  The browser creates
 // a tab for it and responds with a ViewMsg_CreatingNew_ACK.  If route_id is
 // MSG_ROUTING_NONE, the view couldn't be created.
 IPC_SYNC_MESSAGE_CONTROL1_4(ViewHostMsg_CreateWindow,
@@ skipping 692 matching lines @@
 // Since the browser keeps handles to the allocated transport DIBs, this
 // message is sent to tell the browser that it may release them when the
 // renderer is finished with them.
 IPC_MESSAGE_CONTROL1(ViewHostMsg_FreeTransportDIB,
                      TransportDIB::Id /* DIB id */)
 #endif
 
 // Adding a new message? Stick to the sort order above: first platform
 // independent ViewMsg, then ifdefs for platform specific ViewMsg, then platform
 // independent ViewHostMsg, then ifdefs for platform specific ViewHostMsg.