Block NPAPI plug-ins in Metro mode instead of not loading them at all.

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 41 matching lines @@
 
 // This enum is inside a struct so that we can forward-declare the struct in
 // others headers without having to include this one.
 struct ChromeViewHostMsg_GetPluginInfo_Status {
   enum Value {
     kAllowed,
     kBlocked,
     kClickToPlay,
     kDisabled,
     kNotFound,
+    kNPAPINotSupported,
     kOutdatedBlocked,
     kOutdatedDisallowed,
     kUnauthorized,
   };
 
   ChromeViewHostMsg_GetPluginInfo_Status() : value(kAllowed) {}
 
   Value value;
 };
 
@@ skipping 404 matching lines @@
 
 // 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)
 
 // Tells the browser that there was an error loading a plug-in.
 IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_CouldNotLoadPlugin,
                     FilePath /* plugin_path */)
 
+// Tells the browser that we blocked a plug-in because NPAPI is not supported.
+IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_NPAPINotSupported,
+                    std::string /* identifer */)
+
 // Send a snapshot of the tab contents to the render host.
 IPC_MESSAGE_ROUTED1(ChromeViewHostMsg_Snapshot,
                     SkBitmap /* bitmap */)
 
 // A message for an external host.
 IPC_MESSAGE_ROUTED3(ChromeViewHostMsg_ForwardMessageToExternalHost,
                     std::string  /* message */,
                     std::string  /* origin */,
                     std::string  /* target */)
 
@@ 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 */)