Add support for entering/exiting HTML fullscreen from OOPIFs.

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 770 matching lines @@
 // Update a proxy's replicated origin.  Used when the frame is navigated to a
 // new origin.
 IPC_MESSAGE_ROUTED2(FrameMsg_DidUpdateOrigin,
                     url::Origin /* origin */,
                     bool /* is potentially trustworthy unique origin */)
 
 // Notifies this frame or proxy that it is now focused.  This is used to
 // support cross-process focused frame changes.
 IPC_MESSAGE_ROUTED0(FrameMsg_SetFocusedFrame)
 
+// Sent when an element in a cross-process subframe of this frame is preparing
+// to go fullscreen.  |fullscreen_frame_routing_id| identifies the subframe
+// proxy which will contain the fullscreen element.  Actually entering
+// fullscreen will be done separately as part of ViewMsg_Resize, once this
+// frame's widget is resized for fullscreen.
+IPC_MESSAGE_ROUTED1(FrameMsg_WillEnterFullscreen,
+                    int /* fullscreen_frame_routing_id */)
+
 // Send to the RenderFrame to set text tracks state and style settings.
 // Sent for top-level frames.
 IPC_MESSAGE_ROUTED1(FrameMsg_SetTextTrackSettings,
                     FrameMsg_TextTrackSettings_Params /* params */)
 
 // Posts a message from a frame in another process to the current renderer.
 IPC_MESSAGE_ROUTED1(FrameMsg_PostMessageEvent, FrameMsg_PostMessage_Params)
 
 #if defined(OS_ANDROID)
 // Sent when the browser wants the bounding boxes of the current find matches.
@@ skipping 644 matching lines @@
 IPC_MESSAGE_ROUTED3(FrameHostMsg_FindMatchRects_Reply,
                     int /* version */,
                     std::vector<gfx::RectF> /* rects */,
                     gfx::RectF /* active_rect */)
 #endif
 
 // 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.