Implement script-side of callback reactions for Custom Elements V1

third_party/WebKit/Source/bindings/core/v8/V8Binding.h

Index: third_party/WebKit/Source/bindings/core/v8/V8Binding.h
diff --git a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
index e81bdd29998b3d137c3d5cc2807352d5ab37e358..f18e9c4a9ed0bc5ad2d016ae31ccb8b69524a40d 100644
--- a/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
+++ b/third_party/WebKit/Source/bindings/core/v8/V8Binding.h
@@ -407,6 +407,13 @@ inline v8::Local<v8::String> v8String(v8::Isolate* isolate, const String& string
     return V8PerIsolateData::from(isolate)->getStringCache()->v8ExternalString(isolate, string.impl());
 }
 
+inline v8::Local<v8::Value> v8StringOrNull(v8::Isolate* isolate, const AtomicString& string)

[haraken, 2016/06/14 11:39:24]

Do you really need this behavior? "string or null" is not a speced behavior, so
we've tried hard to deprecate this method. And now you're introducing it again
:)

[kojii, 2016/06/14 13:59:43]

The attributeChangedCallback spec says "null" for append/remove case:
https://dom.spec.whatwg.org/#concept-element-attributes-change-ext
and upgrade case:
https://html.spec.whatwg.org/multipage/scripting.html#concept-upgrade-an-element

The append/remove spec above also defines the use of "null" for
MutationObserver. I couldn't figure out how we convert this to v8::Null, but we
seem to work as spec'ed:
http://jsbin.com/tajesihuga

Is this so special and different from other parts of the spec?

+{
+    if (string.isNull())
+        return v8::Null(isolate);
+    return V8PerIsolateData::from(isolate)->getStringCache()->v8ExternalString(isolate, string.impl());
+}
+
 inline v8::Local<v8::String> v8String(v8::Isolate* isolate, const CompressibleString& string)
 {
     if (string.isNull())