Change V8VarConverter::FromV8Value to complete synchronously if possible

content/renderer/pepper/v8_var_converter.h

 // Copyright (c) 2013 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 CONTENT_RENDERER_PEPPER_V8_VAR_CONVERTER_H
 #define CONTENT_RENDERER_PEPPER_V8_VAR_CONVERTER_H
 
 #include "base/basictypes.h"
 #include "base/callback.h"
 #include "base/compiler_specific.h"
 #include "base/message_loop/message_loop_proxy.h"
 #include "ppapi/c/pp_instance.h"
 #include "ppapi/c/pp_var.h"
+#include "ppapi/shared_impl/scoped_pp_var.h"
 #include "v8/include/v8.h"
 #include "content/common/content_export.h"
 
-namespace ppapi {
-class ScopedPPVar;
-}
-
 namespace content {
 
 class ResourceConverter;
 
 class CONTENT_EXPORT V8VarConverter {
  public:
   explicit V8VarConverter(PP_Instance instance);
   // Constructor for testing.
   V8VarConverter(PP_Instance instance,
                  scoped_ptr<ResourceConverter> resource_converter);
   ~V8VarConverter();
 
   // Converts the given PP_Var to a v8::Value. True is returned upon success.
   bool ToV8Value(const PP_Var& var,
                  v8::Handle<v8::Context> context,
                  v8::Handle<v8::Value>* result);
 
+  struct VarResult {
+   public:
+    VarResult() : completed_synchronously(false), success(false) {}
+
+    // True if the conversion completed synchronously and the callback will not
+    // be called.
+    bool completed_synchronously;
+
+    // True if the conversion was successful. Only valid if
+    // |completed_synchronously| is true.
+    bool success;
+
+    // The result if the conversion was successful. Only valid if
+    // |completed_synchronously| and |success| are true.
+    ppapi::ScopedPPVar var;
+  };
+
   // Converts the given v8::Value to a PP_Var. Every PP_Var in the reference
   // graph in the result will have a refcount equal to the number of references
   // to it in the graph. The root of the result will have one additional
   // reference. The callback is run when conversion is complete with the
-  // resulting var and a bool indicating success or failure. Conversion is
+  // resulting var and a bool indicating success or failure. Conversion may be
   // asynchronous because converting some resources may result in communication
-  // across IPC. |context| is guaranteed to only be used synchronously.
-  void FromV8Value(
+  // across IPC. |context| is guaranteed to only be used synchronously. If
+  // the conversion can occur synchronously, |callback| will not be run,
+  // otherwise it will be run.
+  VarResult FromV8Value(
       v8::Handle<v8::Value> val,
       v8::Handle<v8::Context> context,
       const base::Callback<void(const ppapi::ScopedPPVar&, bool)>& callback);
  private:
   // Returns true on success, false on failure.
   bool FromV8ValueInternal(v8::Handle<v8::Value> val,
                            v8::Handle<v8::Context> context,
                            ppapi::ScopedPPVar* result_var);
 
   // The message loop to run the callback to |FromV8Value| from.
   scoped_refptr<base::MessageLoopProxy> message_loop_proxy_;
 
   // The converter to use for converting V8 vars to resources.
   scoped_ptr<ResourceConverter> resource_converter_;
 
   DISALLOW_COPY_AND_ASSIGN(V8VarConverter);
 };
 
 }  // namespace content
 
 #endif  // CONTENT_RENDERER_PEPPER_V8_VAR_CONVERTER_H