Introduce CustomElementRegistry#get() method

third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp

 // Copyright 2016 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.
 
 #include "core/dom/custom/CustomElementsRegistry.h"
 
 // TODO(dominicc): Stop including Document.h when
 // v0CustomElementIsDefined has been removed.
 #include "bindings/core/v8/DOMWrapperWorld.h"
 #include "bindings/core/v8/ExceptionState.h"
@@ skipping 119 matching lines @@
 
     Id id = m_definitions.size();
     v8::Local<v8::Value> idValue = v8::Integer::NewFromUnsigned(isolate, id);
     m_definitions.append(new CustomElementDefinition(this, id, name));
     // This map is stored in a hidden reference from the
     // CustomElementsRegistry wrapper.
     v8::Local<v8::Map> map = idMap(scriptState);
     // The map keeps the constructor and prototypes alive.
     v8CallOrCrash(map->Set(context, constructor, idValue));
     v8CallOrCrash(map->Set(context, idValue, prototype));
-    m_names.add(name);
+    m_names.add(name, id);
 
     // TODO(dominicc): Implement steps:
     // 20: when-defined promise processing
     DCHECK(!tryCatch.HasCaught() || tryCatch.HasTerminated());
 }
 
 CustomElementDefinition* CustomElementsRegistry::definitionForConstructor(
     ScriptState* scriptState,
     v8::Local<v8::Value> constructor)
 {
     Id id;
     if (!idForConstructor(scriptState, constructor, id))
         return nullptr;
     return m_definitions[id];
 }
 
+// http://w3c.github.io/webcomponents/spec/custom/#dom-customelementsregistry-get

[kojii, 2016/05/19 10:04:32]

It's already old, should be:
https://html.spec.whatwg.org/multipage/scripting.html#dom-customelementsregis...

[yosin_UTC9, 2016/05/23 04:45:06]

Done

+ScriptValue CustomElementsRegistry::get(
+    ScriptState* scriptState, const AtomicString& name) const
+{
+    const auto& it = m_names.find(name);
+    if (it == m_names.end())
+        return ScriptValue(scriptState, v8Undefined());
+    v8::Local<v8::Context> context = scriptState->context();

[dominicc (has gone to gerrit), 2016/05/19 22:12:10]

You should CHECK that scriptState->world().isMainWorld(); maybe you could
upgrade the DCHECK in idMap to work in release.

The reason is, if it was not the main world, you would be returning a
constructor in the main world to an isolated world which would be bad--those are
different contexts.

However IIRC the CustomElementsRegistry object can't be retrieved from isolated
worlds, so a check is enough. But make function in release; it really should
never happen.

+    v8::Local<v8::Map> map = idMap(scriptState);
+    v8::Local<v8::Value> idValue = toV8(it->value, scriptState);
+    return ScriptValue(scriptState, v8CallOrCrash(map->Get(context, idValue)));

[dominicc (has gone to gerrit), 2016/05/19 22:12:10]

I believe this is the prototype; not the constructor.

+}
+
 v8::Local<v8::Object> CustomElementsRegistry::prototype(
     ScriptState* scriptState,
     const CustomElementDefinition& def)
 {
     v8::Local<v8::Value> idValue =
         v8::Integer::NewFromUnsigned(scriptState->isolate(), def.id());
     return v8CallOrCrash(
         idMap(scriptState)->Get(scriptState->context(), idValue))
         .As<v8::Object>();
 }
 
 bool CustomElementsRegistry::nameIsDefined(const AtomicString& name) const
 {
     return m_names.contains(name);
 }
 
-v8::Local<v8::Map> CustomElementsRegistry::idMap(ScriptState* scriptState)
+v8::Local<v8::Map> CustomElementsRegistry::idMap(ScriptState* scriptState) const
 {
     DCHECK(scriptState->world().isMainWorld());
     v8::Local<v8::Object> wrapper =
         toV8(this, scriptState).As<v8::Object>();
     v8::Local<v8::String> name = V8HiddenValue::customElementsRegistryMap(
         scriptState->isolate());
     return V8HiddenValue::getHiddenValue(scriptState, wrapper, name)
         .As<v8::Map>();
 }
 
@@ skipping 15 matching lines @@
     return m_v0.get() && m_v0->nameIsDefined(name);
 }
 
 DEFINE_TRACE(CustomElementsRegistry)
 {
     visitor->trace(m_definitions);
     visitor->trace(m_v0);
 }
 
 } // namespace blink