Add Maplike<> utility mixin class for implementing maplike interfaces

Source/modules/webmidi/MIDIInputMap.h

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MIDIInputMap_h
 #define MIDIInputMap_h
 
 #include "bindings/core/v8/ScriptWrappable.h"
 #include "modules/webmidi/MIDIInput.h"
 #include "modules/webmidi/MIDIPortMap.h"
 
 namespace blink {
 
 class ScriptState;
 
 class MIDIInputMap : public MIDIPortMap<MIDIInput>, public ScriptWrappable {
     DEFINE_WRAPPERTYPEINFO();
 public:
     explicit MIDIInputMap(const HeapHashMap<String, Member<MIDIInput>>);
-
-    ScriptValue getForBinding(ScriptState*, const String& id);
 };
 
 } // namespace blink
 
 #endif