Canvas capture from inactive tab

content/common/frame_messages.h

 // Copyright 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 interacting with frames.
 // Multiply-included message file, hence no include guard.
 
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 1414 matching lines @@
 // frame traversal order starting in the main frame, then by dom order.
 //
 // |active_rect| will contain the bounding box of the active find-in-page match
 // marker, in similarly normalized coords (or an empty rect if there isn't one).
 IPC_MESSAGE_ROUTED3(FrameHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 #endif
 
+IPC_MESSAGE_ROUTED0(FrameHostMsg_IncrementCapturerCount)
+IPC_MESSAGE_ROUTED0(FrameHostMsg_DecrementCapturerCount)
+
 // Adding a new message? Stick to the sort order above: first platform
 // independent FrameMsg, then ifdefs for platform specific FrameMsg, then
 // platform independent FrameHostMsg, then ifdefs for platform specific
 // FrameHostMsg.