Keep event page alive when there's some Pepper plugin on it.

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 "content/common/content_export.h"
 #include "content/common/content_param_traits.h"
 #include "content/common/frame_message_enums.h"
@@ skipping 702 matching lines @@
 // Following message is used to communicate the values received by the
 // callback binding the JS to Cpp.
 // An instance of browser that has an automation host listening to it can
 // have a javascript send a native value (string, number, boolean) to the
 // listener in Cpp. (DomAutomationController)
 IPC_MESSAGE_ROUTED2(FrameHostMsg_DomOperationResponse,
                     std::string  /* json_string */,
                     int  /* automation_id */)
 
 #if defined(ENABLE_PLUGINS)
+// Notification sent from a renderer to the browser that a Pepper plugin
+// instance is created in the DOM.
+IPC_MESSAGE_ROUTED0(FrameHostMsg_PepperInstanceCreated)
+
+// Notification sent from a renderer to the browser that a Pepper plugin
+// instance is deleted from the DOM.
+IPC_MESSAGE_ROUTED0(FrameHostMsg_PepperInstanceDeleted)
+
 // Sent to the browser when the renderer detects it is blocked on a pepper
 // plugin message for too long. This is also sent when it becomes unhung
 // (according to the value of is_hung). The browser can give the user the
 // option of killing the plugin.
 IPC_MESSAGE_ROUTED3(FrameHostMsg_PepperPluginHung,
                     int /* plugin_child_id */,
                     base::FilePath /* path */,
                     bool /* is_hung */)
 
 // Sent by the renderer process to indicate that a plugin instance has crashed.
@@ skipping 173 matching lines @@
                     FrameMsg_PostMessage_Params)
 
 #if defined(OS_MACOSX) || defined(OS_ANDROID)
 
 // Message to show/hide a popup menu using native controls.
 IPC_MESSAGE_ROUTED1(FrameHostMsg_ShowPopup,
                     FrameHostMsg_ShowPopup_Params)
 IPC_MESSAGE_ROUTED0(FrameHostMsg_HidePopup)
 
 #endif