Implemented GetWindowSnapshot on RenderViewImpl

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/process.h"
 #include "base/shared_memory.h"
 #include "content/common/content_export.h"
@@ skipping 1911 matching lines @@
 IPC_MESSAGE_ROUTED1(ViewHostMsg_HasTouchEventHandlers,
                     bool /* has_handlers */)
 
 // A message from HTML-based UI.  When (trusted) Javascript calls
 // send(message, args), this message is sent to the browser.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_WebUISend,
                     GURL /* source_url */,
                     std::string  /* message */,
                     base::ListValue /* args */)
 
+// Requests a snapshot of the given window.
+IPC_MESSAGE_ROUTED1(ViewHostMsg_GetWindowSnapshot,
+                    int /* message id */)
+
+// Notifies the render view that a snapshot has been retrieved.
+IPC_MESSAGE_ROUTED3(ViewMsg_WindowSnapshotCompleted,

[jam, 2012/11/15 01:05:59]

nit: this should go with the rest of the browser->renderer message above this
section (i.e. line 1432)

+                    int /* snapshot_id */,
+                    gfx::Size /* size */,
+                    std::vector<unsigned char> /* png */)
+
 // A renderer sends this to the browser process when it wants to create a ppapi
 // plugin.  The browser will create the plugin process if necessary, and will
 // return a handle to the channel on success.
 //
 // The plugin_child_id is the ChildProcessHost ID assigned in the browser
 // process. This ID is valid only in the context of the browser process and is
 // used to identify the proper process when the renderer notifies it that the
 // plugin is hung.
 //
 // On error an empty string and null handles are returned.
@@ skipping 455 matching lines @@
 IPC_MESSAGE_ROUTED1(ViewHostMsg_StartContentIntent,
                     GURL /* content_url */)
 #endif
 
 // Notifies that multiple touch targets may have been pressed, and to show
 // the disambiguation popup.
 IPC_MESSAGE_ROUTED3(ViewHostMsg_ShowDisambiguationPopup,
                     gfx::Rect, /* Border of touched targets */
                     gfx::Size, /* Size of zoomed image */
                     TransportDIB::Id /* DIB of zoomed image */)