Enable fire-and-forget Destroy of HW video decoder, and misc other improvements.

webkit/plugins/ppapi/plugin_delegate.h

Index: webkit/plugins/ppapi/plugin_delegate.h
diff --git a/webkit/plugins/ppapi/plugin_delegate.h b/webkit/plugins/ppapi/plugin_delegate.h
index dae68a86648f93f9fdf98b9e0d298852e440687b..2b6e09878548b990fd31104f7b155f1fdd67126e 100644
--- a/webkit/plugins/ppapi/plugin_delegate.h
+++ b/webkit/plugins/ppapi/plugin_delegate.h
@@ -216,7 +216,7 @@ class PluginDelegate {
   // Interface for PlatformVideoDecoder is directly inherited from general media
   // VideoDecodeAccelerator interface.
   class PlatformVideoDecoder : public media::VideoDecodeAccelerator {
-   public:
+   protected:
     virtual ~PlatformVideoDecoder() {}
   };