WIP bindings: Add support for the record<K,V> WebIDL type.

third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl

Index: third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl
diff --git a/third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl b/third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl
index 3681457ff617e2e3b26598259dc3fa4203869a66..b825a8e20868867a94f1eddd694343f9f6182736 100644
--- a/third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl
+++ b/third_party/WebKit/Source/bindings/templates/dictionary_v8.h.tmpl
@@ -31,7 +31,8 @@ inline void v8SetReturnValue(const CallbackInfo& callbackInfo, {{cpp_class}}& im
 
 template <>
 struct NativeValueTraits<{{cpp_class}}> {
-  static {{cpp_class}} nativeValue(v8::Isolate*, v8::Local<v8::Value>, ExceptionState&);
+  using ImplType = {{cpp_class}};

[Yuki, 2017/03/02 07:47:28]

nit: Can we have this declaration as the default definition of ImplType in
NativeValueTraits.h ?

[Raphael Kubo da Costa (rakuco), 2017/03/02 08:16:24]

I tried doing that earlier, but any template specialization hides the definition
so it didn't work and I had to add those back.

[Yuki, 2017/03/02 13:00:25]

I guess that the following would work.

  template <typename T>
  struct NativeValueTraitsBase {
    using ImplType = T;
  };

  template <typename T>
  struct NativeValueTraits : public NativeValueTraitsBase<T> {
     // ...
  };

  template <>
  struct NativeValueTraits<ActualType> : public
NativeValueTraitsBase<ActualType> {
    // ...
  };

Having said that, it's not shorter than the current CL, although we can easily
add more things in NativeValueTraitsBase.  I'm fine with either way.

+  {{exported}}static {{cpp_class}} nativeValue(v8::Isolate*, v8::Local<v8::Value>, ExceptionState&);
 };
 
 template <>