Make CustomElementsRegistry lazily initialize script state.

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
index de7d2aaa98ccb722181a7683df4dfefd92421b95..c55a0453b495acff8cae4dc916f61873521b1708 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementsRegistry.h
@@ -29,9 +29,8 @@ class CORE_EXPORT CustomElementsRegistry final
     DEFINE_WRAPPERTYPEINFO();
 public:
     using Id = uint32_t;
-    static CustomElementsRegistry* create(
-        ScriptState*,
-        V0CustomElementRegistrationContext*);
+
+    static CustomElementsRegistry* create(V0CustomElementRegistrationContext*);
 
     void define(
         ScriptState*,
@@ -55,10 +54,13 @@ public:
 private:
     CustomElementsRegistry(const V0CustomElementRegistrationContext*);
 
+    // Initializes the state which is kept in the V8 heap. Initializes
+    // the map handle to the constructor->id, id->prototype map; see
+    // idMap.
+    void initializeScript(ScriptState*, v8::Local<v8::Map>&);

[esprehn, 2016/05/23 21:45:17]

add variable name for the map, only leave off the name when the type of the
variable explains what it is. I guess idMap ?

+
     // Retrieves the Map which, given a constructor, contains the id
     // of the definition; or given an id, contains the prototype.
-    // Returns true if the map was retrieved; false if the map was
-    // not initialized yet.
     v8::Local<v8::Map> idMap(ScriptState*);
 
     bool idForConstructor(