Custom Elements: The 'is' Attribute Should Not Be Specified on an Autonomous Custom Element

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 3e4500166cbf47f1a43ffd76d75844346638b1a7..4d3cc4ae6f05aa9b8a19676f9ee52f0c2c5ebd8a 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementRegistry.cpp
@@ -214,12 +214,16 @@ ScriptValue CustomElementRegistry::get(const AtomicString& name) {
 // At this point, what the spec calls 'is' is 'name' from desc
 CustomElementDefinition* CustomElementRegistry::definitionFor(
     const CustomElementDescriptor& desc) const {
-  // 4&5. If there is a definition in registry with name equal to is/localName
-  // Autonomous elements have the same name and local name
-  CustomElementDefinition* definition = definitionForName(desc.name());
-  // 4&5. and name equal to localName, return that definition
-  if (definition and definition->descriptor().localName() == desc.localName())
+  // desc.name() is 'is' attribute
+  // 4. If definition in registry with name equal to local name...
+  CustomElementDefinition* definition = definitionForName(desc.localName());
+  // 5. If definition in registry with name equal to name...
+  if (!definition)
+    definition = definitionForName(desc.name());
+  // 4&5. ...and local name equal to localName, return that definition
+  if (definition and definition->descriptor().localName() == desc.localName()) {
     return definition;
+  }
   // 6. Return null
   return nullptr;
 }