[bindings] Make all CustomEvent.initCustomEvent arguments non-optional and remove custom binding.

Source/bindings/core/v8/custom/V8CustomEventCustom.cpp

 /*
  * Copyright (C) 2012 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 55 matching lines @@
     if (SerializedScriptValue* serializedValue = event->serializedDetail())
         detail = serializedValue->deserialize();
     else
         detail = event->detail().v8ValueFor(ScriptState::current(info.GetIsolate()));
     // |detail| should be null when it is an empty handle because its default value is null.
     if (detail.IsEmpty())
         detail = v8::Null(info.GetIsolate());
     v8SetReturnValue(info, cacheState(info.GetIsolate(), info.Holder(), detail));
 }
 
-void V8CustomEvent::initCustomEventMethodCustom(const v8::FunctionCallbackInfo<v8::Value>& info)
-{
-    CustomEvent* event = V8CustomEvent::toImpl(info.Holder());
-
-    TOSTRING_VOID(V8StringResource<>, typeArg, info[0]);
-    bool canBubbleArg;
-    bool cancelableArg;
-    if (!v8Call(info[1]->BooleanValue(info.GetIsolate()->GetCurrentContext()), canBubbleArg)
-        || !v8Call(info[2]->BooleanValue(info.GetIsolate()->GetCurrentContext()), cancelableArg))
-        return;
-    v8::Local<v8::Value> detailsArg = info[3];
-
-    event->initEvent(typeArg, canBubbleArg, cancelableArg);
-    event->setDetail(ScriptValue(ScriptState::current(info.GetIsolate()), detailsArg));
-}
-
 } // namespace blink