Add blink-side binding code and tests for ServiceWorker -> Document postMessage (3/3)

Source/bindings/bindings.gypi

 {
     'variables': {
         'bindings_v8_dir': 'v8',
         'blink_output_dir': '<(SHARED_INTERMEDIATE_DIR)/blink',
         'bindings_output_dir': '<(SHARED_INTERMEDIATE_DIR)/blink/bindings',
         'bindings_files': [
             'v8/ActiveDOMCallback.cpp',
             'v8/ActiveDOMCallback.h',
             'v8/ArrayValue.cpp',
             'v8/ArrayValue.h',
@@ skipping 143 matching lines @@
             'v8/custom/V8ArrayBufferViewCustom.cpp',
             'v8/custom/V8ArrayBufferViewCustom.h',
             'v8/custom/V8AudioNodeCustom.cpp',
             'v8/custom/V8BlobCustom.cpp',
             'v8/custom/V8BlobCustomHelpers.cpp',
             'v8/custom/V8BlobCustomHelpers.h',
             'v8/custom/V8CSSRuleCustom.cpp',
             'v8/custom/V8CSSStyleDeclarationCustom.cpp',
             'v8/custom/V8CSSValueCustom.cpp',
             'v8/custom/V8CanvasRenderingContext2DCustom.cpp',
+            'v8/custom/V8ClientCustom.cpp',
             'v8/custom/V8CryptoCustom.cpp',
             'v8/custom/V8CustomEventCustom.cpp',
             'v8/custom/V8CustomSQLStatementErrorCallback.cpp',
             'v8/custom/V8CustomXPathNSResolver.cpp',
             'v8/custom/V8CustomXPathNSResolver.h',
             'v8/custom/V8DataViewCustom.cpp',
             'v8/custom/V8DataViewCustom.h',
             'v8/custom/V8DedicatedWorkerGlobalScopeCustom.cpp',
             'v8/custom/V8DeviceMotionEventCustom.cpp',
             'v8/custom/V8DeviceOrientationEventCustom.cpp',
@@ skipping 128 matching lines @@
             # supports this use case (gyp turns all actions into ninja restat
             # rules).
             ['"<(GENERATOR)"=="ninja"', {
               'write_file_only_if_changed': '1',
             }, {
               'write_file_only_if_changed': '0',
             }],
         ],
     },
 }