Inform webkit when PPAPI plugin contents are opaque.

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 985ff9864f7addef73a1226f688a1cfb7752a035..d9d4f10be459b3a7aa472b746f229e8958ee6c3f 100644
--- a/webkit/plugins/ppapi/plugin_delegate.h
+++ b/webkit/plugins/ppapi/plugin_delegate.h
@@ -171,6 +171,9 @@ class PluginDelegate {
     // compositors namespace. Otherwise return 0. Returns 0 by default.
     virtual unsigned GetBackingTextureId() = 0;
 
+    // Returns true if the backing texture is always opaque.
+    virtual bool IsOpaque() = 0;
+
     // This call will return the address of the command buffer for this context
     // that is constructed in Initialize() and is valid until this context is
     // destroyed.