Replace hand-written IDBObserverCallback with auto-generated code

third_party/WebKit/Source/bindings/modules/v8/generated.gni

 # 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.
 
 import("//build/config/chrome_build.gni")
 import("//third_party/WebKit/Source/bindings/bindings.gni")
 import("//third_party/WebKit/Source/core/core_idl_files.gni")
 import("//third_party/WebKit/Source/modules/modules_idl_files.gni")
 
 bindings_modules_v8_output_dir = "$bindings_output_dir/modules/v8"
@@ skipping 46 matching lines @@
   "$bindings_modules_v8_output_dir/StringOrStringSequenceOrConstrainDOMStringParameters.cpp",
   "$bindings_modules_v8_output_dir/StringOrStringSequenceOrConstrainDOMStringParameters.h",
   "$bindings_modules_v8_output_dir/StringOrStringSequenceOrDOMStringList.cpp",
   "$bindings_modules_v8_output_dir/StringOrStringSequenceOrDOMStringList.h",
   "$bindings_modules_v8_output_dir/StringOrUnsignedLong.cpp",
   "$bindings_modules_v8_output_dir/StringOrUnsignedLong.h",
   "$bindings_modules_v8_output_dir/UnsignedLongOrUnsignedLongSequence.cpp",
   "$bindings_modules_v8_output_dir/UnsignedLongOrUnsignedLongSequence.h",
 ]
 
+generated_modules_callback_function_files = [
+  "$bindings_modules_v8_output_dir/IDBObserverCallback.cpp",
+  "$bindings_modules_v8_output_dir/IDBObserverCallback.h",
+]
+
 bindings_modules_generated_interface_files =
     process_file_template(
         modules_definition_idl_files,
         [
           "$bindings_modules_v8_output_dir/V8{{source_name_part}}.cpp",
           "$bindings_modules_v8_output_dir/V8{{source_name_part}}.h",
         ])
 
 bindings_modules_generated_partial_interface_files =
     process_file_template(
         core_idl_with_modules_dependency_files,
         [
           "$bindings_modules_v8_output_dir/V8{{source_name_part}}Partial.cpp",
           "$bindings_modules_v8_output_dir/V8{{source_name_part}}Partial.h",
         ])