[bindings] Include copyright block in generated code for consistency.

Source/bindings/templates/callback_interface.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.
-
-// This file has been auto-generated by {{code_generator}}. DO NOT MODIFY!
-
+{% include 'copyright_block.txt' %}
 #ifndef {{v8_class}}_h
 #define {{v8_class}}_h
 
 {% filter conditional(conditional_string) %}
 {% for filename in header_includes %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
 
@@ skipping 15 matching lines @@
 private:
     {{exported}}{{v8_class}}(v8::Local<v8::Function>, ScriptState*);
 
     ScopedPersistent<v8::Function> m_callback;
     RefPtr<ScriptState> m_scriptState;
 };
 
 }
 {% endfilter %}
 #endif // {{v8_class}}_h