Introduce CustomElementRegistry#get() method

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
index 6163dced4530d47532ca1639222c3e9ac9f85fd2..a6206a8d2eb053bf3e4b4cdddf4e1596182502f5 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.cpp
@@ -137,7 +137,7 @@ void CustomElementsRegistry::define(ScriptState* 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
@@ -154,6 +154,19 @@ CustomElementDefinition* CustomElementsRegistry::definitionForConstructor(
     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)
@@ -170,7 +183,7 @@ 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 =