Enable extension APIs for content scripts.

chrome/common/extensions/extension_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 extensions.
 // Multiply-included message file, hence no include guard.
 
 #include "base/shared_memory.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension.h"
 #include "chrome/common/extensions/extension_permission_set.h"
 #include "chrome/common/extensions/url_pattern.h"
 #include "chrome/common/extensions/url_pattern_set.h"
 #include "chrome/common/web_apps.h"
 #include "content/public/common/view_types.h"
 #include "ipc/ipc_message_macros.h"
 
 #define IPC_MESSAGE_START ExtensionMsgStart
 
 // Parameters structure for ExtensionHostMsg_Request.
 IPC_STRUCT_BEGIN(ExtensionHostMsg_Request_Params)
   // Message name.
   IPC_STRUCT_MEMBER(std::string, name)
 
   // List of message arguments.
   IPC_STRUCT_MEMBER(ListValue, arguments)
 
-  // URL of the frame request was sent from.
+  // Extension ID this request was sent from. This can be empty, in the case
+  // where we expose APIs to normal web pages using the extension function
+  // system.
+  IPC_STRUCT_MEMBER(std::string, extension_id)
+
+  // URL of the frame the request was sent from. This isn't necessarily an
+  // extension url. Extension requests can also originate from content scripts,
+  // in which case extension_id will indicate the ID of the associated
+  // extension. Or, they can origiante from hosted apps or normal web pages.
   IPC_STRUCT_MEMBER(GURL, source_url)
 
   // Unique request id to match requests and responses.
   IPC_STRUCT_MEMBER(int, request_id)
 
   // True if request has a callback specified.
   IPC_STRUCT_MEMBER(bool, has_callback)
 
   // True if request is executed in response to an explicit user gesture.
   IPC_STRUCT_MEMBER(bool, user_gesture)
@@ skipping 312 matching lines @@
 // Response to the renderer for the above message.
 IPC_MESSAGE_ROUTED3(ExtensionMsg_GetAppNotifyChannelResponse,
                     std::string /* channel_id */,
                     std::string /* error */,
                     int32 /* callback_id */)
 
 // Deliver a message sent with ExtensionHostMsg_PostMessage.
 IPC_MESSAGE_ROUTED2(ExtensionMsg_DeliverMessage,
                     int /* target_port_id */,
                     std::string /* message */)