Custom Elements: Lookup custom element definition algorithm

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp b/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
index 0e703cad458ebf76c73dec97eca5604fcd7284f7..7ad996976d8534e102382e6414c79df8bf952aca 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
@@ -194,16 +194,22 @@ ScriptValue CustomElementRegistry::get(const AtomicString& name) {
   return definition->getConstructorForScript();
 }
 
+// https://html.spec.whatwg.org/multipage/scripting.html#look-up-a-custom-element-definition
+// At this point, what the spec calls 'is' is 'name' from desc
 CustomElementDefinition* CustomElementRegistry::definitionFor(
     const CustomElementDescriptor& desc) const {
-  CustomElementDefinition* definition = definitionForName(desc.name());
-  if (!definition)
-    return nullptr;
-  // The definition for a customized built-in element, such as
-  // <button is="my-button"> should not be provided for an
-  // autonomous element, such as <my-button>, even though the
-  // name "my-button" matches.
-  return definition->descriptor() == desc ? definition : nullptr;
+  // 4. If there is a definition in registry with name equal to localName and

[dominicc (has gone to gerrit), 2016/10/27 04:33:14]

Try to write this with only one lookup with definitionForName. Note: localName
== name for autonomous custom elements.

+  // local name equal to localName, return that definition
+  CustomElementDefinition* definition = definitionForName(desc.localName());
+  if (definition and definition->descriptor().localName() == desc.localName())
+    return definition;
+  // 5. If there is a definition in registry with name equal to is and local
+  // name equal to localName, return that definition
+  definition = definitionForName(desc.name());
+  if (definition and definition->descriptor().localName() == desc.localName())
+    return definition;
+  // 6. Return null
+  return nullptr;
 }
 
 bool CustomElementRegistry::nameIsDefined(const AtomicString& name) const {