Enabling page visibility api in the chrome browser.

content/common/view_messages.h

 // Copyright (c) 2011 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/common_param_traits.h"
@@ skipping 676 matching lines @@
   IPC_STRUCT_MEMBER(std::string, state)
 
   // Type of navigation.
   IPC_STRUCT_MEMBER(ViewMsg_Navigate_Type::Value, navigation_type)
 
   // The time the request was created
   IPC_STRUCT_MEMBER(base::Time, request_time)
 
   // Extra headers (separated by \n) to send during the request.
   IPC_STRUCT_MEMBER(std::string, extra_headers)
+
+  // Is the tab containing the corresponding rvh visible?
+  IPC_STRUCT_MEMBER(bool, is_hidden)
 IPC_STRUCT_END()
 
 IPC_STRUCT_BEGIN(ViewMsg_New_Params)
   // The parent window's id.
   IPC_STRUCT_MEMBER(gfx::NativeViewId, parent_window)
 
   // Surface for accelerated rendering.
   IPC_STRUCT_MEMBER(gfx::PluginWindowHandle, compositing_surface)
 
   // Renderer-wide preferences.
@@ skipping 1233 matching lines @@
 
 // Stores new inspector setting in the profile.
 // TODO(jam): this should be in the chrome module
 IPC_MESSAGE_ROUTED2(ViewHostMsg_UpdateInspectorSetting,
                     std::string,  /* key */
                     std::string /* value */)
 
 // Send back a string to be recorded by UserMetrics.
 IPC_MESSAGE_CONTROL1(ViewHostMsg_UserMetricsRecordAction,
                      std::string /* action */)