Take 2 at implementing activeTab.

chrome/common/extensions/extension_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 extensions.
 // Multiply-included message file, hence no include guard.
 
 #include "base/shared_memory.h"
 #include "base/values.h"
 #include "chrome/common/extensions/extension.h"
@@ skipping 216 matching lines @@
 // SharedMemoryHandle argument consisting of the pickled script data. This
 // handle is valid in the context of the renderer.
 IPC_MESSAGE_CONTROL1(ExtensionMsg_UpdateUserScripts,
                      base::SharedMemoryHandle)
 
 // Requests application info for the page. The renderer responds back with
 // ExtensionHostMsg_DidGetApplicationInfo.
 IPC_MESSAGE_ROUTED1(ExtensionMsg_GetApplicationInfo,
                     int32 /*page_id*/)
 
-// Tell the renderer which browser window it's being attached to.
+// Tell the render view which browser window it's being attached to.
 IPC_MESSAGE_ROUTED1(ExtensionMsg_UpdateBrowserWindowId,
                     int /* id of browser window */)
 
+// Tell the render view what its tab ID is.
+IPC_MESSAGE_ROUTED1(ExtensionMsg_SetTabId,
+                    int /* id of tab */)
+
 // Tell the renderer to update an extension's permission set.
 IPC_MESSAGE_CONTROL5(ExtensionMsg_UpdatePermissions,
                      int /* UpdateExtensionPermissionsInfo::REASON */,
                      std::string /* extension_id */,
                      ExtensionAPIPermissionSet /* permissions */,
                      URLPatternSet /* explicit_hosts */,
                      URLPatternSet /* scriptable_hosts */)
 
+// Tell the renderer about new tab-specific permissions for an extension.
+IPC_MESSAGE_CONTROL4(ExtensionMsg_UpdateTabSpecificPermissions,
+                     int32 /* page_id (only relevant for the target tab) */,
+                     int /* tab_id */,
+                     std::string /* extension_id */,
+                     URLPatternSet /* host */)
+
+// Tell the renderer to clear tab-specific permissions for some extensions.
+IPC_MESSAGE_CONTROL2(ExtensionMsg_ClearTabSpecificPermissions,
+                     int /* tab_id */,
+                     std::vector<std::string> /* extension_ids */)
+
 // Tell the renderer which type this view is.
 IPC_MESSAGE_ROUTED1(ExtensionMsg_NotifyRenderViewType,
                     chrome::ViewType /* view_type */)
 
 // Deliver a message sent with ExtensionHostMsg_PostMessage.
 IPC_MESSAGE_CONTROL3(ExtensionMsg_UsingWebRequestAPI,
                      bool /* adblock */,
                      bool /* adblock_plus */,
                      bool /* other_webrequest */)
 
@@ skipping 190 matching lines @@
 IPC_MESSAGE_ROUTED0(ExtensionHostMsg_IncrementLazyKeepaliveCount)
 
 // Informs the browser there is one less thing keeping the lazy background page
 // alive.
 IPC_MESSAGE_ROUTED0(ExtensionHostMsg_DecrementLazyKeepaliveCount)
 
 // Fetches a globally unique ID (for the lifetime of the browser) from the
 // browser process.
 IPC_SYNC_MESSAGE_CONTROL0_1(ExtensionHostMsg_GenerateUniqueID,
                             int /* unique_id */)