Introduce CustomElementRegistry#get() method

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

Index: third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
diff --git a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
index e410349ac24f66484daacbb7c199e68be1822b60..1406052c0f5ca0e157603406f1e315f5d0dc1c40 100644
--- a/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
+++ b/third_party/WebKit/Source/core/dom/custom/CustomElementDefinition.h
@@ -5,6 +5,7 @@
 #ifndef CustomElementDefinition_h
 #define CustomElementDefinition_h
 
+#include "bindings/core/v8/ScriptValue.h"
 #include "core/CoreExport.h"
 #include "core/dom/custom/CustomElementDescriptor.h"
 #include "platform/heap/Handle.h"
@@ -12,6 +13,8 @@
 
 namespace blink {
 
+class ScriptState;
+
 class CORE_EXPORT CustomElementDefinition
     : public GarbageCollectedFinalized<CustomElementDefinition> {
     WTF_MAKE_NONCOPYABLE(CustomElementDefinition);
@@ -21,6 +24,11 @@ public:
 
     const CustomElementDescriptor& descriptor() { return m_descriptor; }
 
+    // TODO(yosin): We should ask binding layer to convert C++ constructor

[dominicc (has gone to gerrit), 2016/05/31 22:56:32]

This TODO covers "what"--ask the binding layer to convert C++ constructors.

What's missing is a "when" and/or "why". Try to include some detail that's the
trigger condition, so a knowledgable reader can say "ah, we can fix this TODO
now" or "no, this is still blocked because X."

+    // value to ScriptValue, e.g. introduce |CustomElementConsturcotr|

[dominicc (has gone to gerrit), 2016/05/31 22:56:32]

spelling: constructor

[yosin_UTC9, 2016/06/01 02:14:37]

Done.

+    // class with |ScripttCustomElementConsturcotr|

[dominicc (has gone to gerrit), 2016/05/31 22:56:32]

spelling: script, constructor

[yosin_UTC9, 2016/06/01 02:14:37]

Done.

+    virtual ScriptValue getConstructor(ScriptState*) = 0;

[dominicc (has gone to gerrit), 2016/05/31 22:56:32]

What do you think about calling this getConstructorForScript or
getScriptConstructor? This method is all about interfacing with JavaScript, we
may as well put it right in the name.

[yosin_UTC9, 2016/06/01 02:14:37]

Done. Use getConstructorForScript()

+
     DEFINE_INLINE_VIRTUAL_TRACE() { }
 
 private: