PPAPI: Implement synchronous postMessage

content/renderer/pepper/resource_converter.h

Index: content/renderer/pepper/resource_converter.h
diff --git a/content/renderer/pepper/resource_converter.h b/content/renderer/pepper/resource_converter.h
index 5b46adf4c533b1866a7a4e07eca00a1d18845ca6..47493bf31dd7b754f8c95f229aac0fbb684143d9 100644
--- a/content/renderer/pepper/resource_converter.h
+++ b/content/renderer/pepper/resource_converter.h
@@ -34,9 +34,11 @@ class CONTENT_EXPORT ResourceConverter {
  public:
   virtual ~ResourceConverter();
 
-  // Flush() must be called before any vars created by the ResourceConverter
-  // are valid. It handles creating any resource hosts that need to be created.
+  // Flush() or FlushSync() must be called before any vars created by the
+  // ResourceConverter are valid. They handle creating any resource hosts that
+  // need to be created.
   virtual void Flush(const base::Callback<void(bool)>& callback) = 0;
+  virtual bool FlushSync() = 0;
 
   // Attempts to convert a V8 object to a PP_Var with type PP_VARTYPE_RESOURCE.
   // On success, writes the resulting var to |result|, sets |was_resource| to
@@ -62,6 +64,7 @@ class ResourceConverterImpl : public ResourceConverter {
 
   // ResourceConverter overrides.
   virtual void Flush(const base::Callback<void(bool)>& callback) OVERRIDE;
+  virtual bool FlushSync() OVERRIDE;
   virtual bool FromV8Value(v8::Handle<v8::Object> val,
                            v8::Handle<v8::Context> context,
                            PP_Var* result,