Implement script-side of callback reactions for Custom Elements V1

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

 /*
 * Copyright (C) 2009 Google Inc. All rights reserved.
 * Copyright (C) 2012 Ericsson AB. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 *
 *     * Redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer.
@@ skipping 389 matching lines @@
 // Return a V8 external string that shares the underlying buffer with the given
 // WebCore string. The reference counting mechanism is used to keep the
 // underlying buffer alive while the string is still live in the V8 engine.
 inline v8::Local<v8::String> v8String(v8::Isolate* isolate, const String& string)
 {
     if (string.isNull())
         return v8::String::Empty(isolate);
     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())
         return v8::String::Empty(isolate);
     return V8PerIsolateData::from(isolate)->getStringCache()->v8ExternalString(isolate, string);
 }
 
 inline v8::Local<v8::String> v8AtomicString(v8::Isolate* isolate, const char* str, int length = -1)
 {
     ASSERT(isolate);
@@ skipping 543 matching lines @@
 typedef void (*InstallTemplateFunction)(v8::Isolate*, const DOMWrapperWorld&, v8::Local<v8::FunctionTemplate> interfaceTemplate);
 
 // Freeze a V8 object. The type of the first parameter and the return value is
 // intentionally v8::Value so that this function can wrap toV8().
 // If the argument isn't an object, this will crash.
 CORE_EXPORT v8::Local<v8::Value> freezeV8Object(v8::Local<v8::Value>, v8::Isolate*);
 
 } // namespace blink
 
 #endif // V8Binding_h