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

Source/bindings/templates/union.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 {{macro_guard}}
 #define {{macro_guard}}
 
 {% for filename in header_includes %}
 #include "{{filename}}"
 {% endfor %}
 
 namespace blink {
 
 {% for decl in header_forward_decls %}
@@ skipping 71 matching lines @@
         if (isUndefinedOrNull(v8Value))
             return;
         V8{{cpp_type}}::toImpl(isolate, v8Value, impl, exceptionState);
     }
 };
 
 {% endfor %}
 } // namespace blink
 
 #endif // {{macro_guard}}