Add IPC message to open chrome://plugins from a missing plug-in placeholder.

chrome/common/render_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.
 
 // Multiply-included file, no traditional include guard.
 #include <map>
 #include <set>
 #include <string>
 #include <vector>
 
@@ skipping 428 matching lines @@
 // Notifies a missing plug-in placeholder that no plug-in has been found.
 IPC_MESSAGE_ROUTED0(ChromeViewMsg_DidNotFindMissingPlugin)
 
 // Notifies a missing plug-in placeholder that we have started downloading
 // the plug-in.
 IPC_MESSAGE_ROUTED0(ChromeViewMsg_StartedDownloadingPlugin)
 
 // Notifies a missing plug-in placeholder that we have finished downloading
 // the plug-in.
 IPC_MESSAGE_ROUTED0(ChromeViewMsg_FinishedDownloadingPlugin)
-#endif  // defined(ENABLE_PLUGIN_INSTALLATION)
 
 // Notifies a missing plug-in placeholder that there was an error downloading
 // the plug-in.
 IPC_MESSAGE_ROUTED1(ChromeViewMsg_ErrorDownloadingPlugin,
                     std::string /* message */)
+#endif  // defined(ENABLE_PLUGIN_INSTALLATION)
+
+// Tells the browser to open chrome://plugins in a new tab. We use a separate
+// message because renderer processes aren't allowed to directly navigate to
+// chrome:// URLs.
+IPC_MESSAGE_ROUTED0(ChromeViewHostMsg_OpenAboutPlugins)
 
 // Specifies the URL as the first parameter (a wstring) and thumbnail as
 // binary data as the second parameter.
 IPC_MESSAGE_ROUTED3(ChromeViewHostMsg_Thumbnail,
                     GURL /* url */,
                     ThumbnailScore /* score */,
                     SkBitmap /* bitmap */)
 
 // Send a snapshot of the tab contents to the render host.
 IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_Snapshot,
@@ skipping 152 matching lines @@
 // previous SetCookie message to be processed.
 IPC_SYNC_MESSAGE_ROUTED2_1(ChromeViewHostMsg_GetCookies,
                            GURL /* url */,
                            GURL /* first_party_for_cookies */,
                            std::string /* cookies */)
 
 // Provide the browser process with current renderer framerate.
 IPC_MESSAGE_CONTROL2(ChromeViewHostMsg_FPS,
                      int /* routing id */,
                      float /* frames per second */)