npapi plugins: Make sure WebPlugin has no key functions on mac.

webkit/plugins/npapi/webplugin.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.
 
 #ifndef WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_H_
 #define WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 139 matching lines @@
   // Synthesize a fake window handle for the plug-in to identify the instance
   // to the browser, allowing mapping to a surface for hardware accelleration
   // of plug-in content. The browser generates the handle which is then set on
   // the plug-in. |opaque| indicates whether the content should be treated as
   // opaque or translucent.
   // TODO(stuartmorgan): Move this into WebPluginProxy.
   virtual void BindFakePluginWindowHandle(bool opaque) {}
 
   // Returns the accelerated surface abstraction for accelerated plugins.
   virtual WebPluginAcceleratedSurface* GetAcceleratedSurface(
-      gfx::GpuPreference gpu_preference);
+      gfx::GpuPreference gpu_preference) = 0;
 
   // Composited Core Animation plugin support.
   virtual void AcceleratedPluginEnabledRendering() = 0;
   virtual void AcceleratedPluginAllocatedIOSurface(int32 width,
                                                    int32 height,
                                                    uint32 surface_id) = 0;
   virtual void AcceleratedPluginSwappedIOSurface() = 0;
 #endif
 
   // Handles NPN_URLRedirectResponse calls issued by plugins in response to
@@ skipping 18 matching lines @@
   virtual void DidFinishLoading() = 0;
   virtual void DidFail() = 0;
   virtual bool IsMultiByteResponseExpected() = 0;
   virtual int ResourceId() = 0;
 };
 
 }  // namespace npapi
 }  // namespace webkit
 
 #endif  // WEBKIT_PLUGINS_NPAPI_WEBPLUGIN_H_