[DevTools] Merge InspectorFrontendClientImpl into WebDevToolsFrontendImpl and remove unused code.

Source/web/web.gypi

 {
   'variables': {
     'web_files': [
       'AssertMatchingEnums.cpp',
       'AssociatedURLLoader.cpp',
       'AssociatedURLLoader.h',
       'BackForwardClientImpl.cpp',
       'BackForwardClientImpl.h',
       'ChromeClientImpl.cpp',
       'ChromeClientImpl.h',
@@ skipping 27 matching lines @@
       'FullscreenController.cpp',
       'FullscreenController.h',
       'GeolocationClientProxy.cpp',
       'GeolocationClientProxy.h',
       'GraphicsLayerFactoryChromium.cpp',
       'GraphicsLayerFactoryChromium.h',
       'IndexedDBClientImpl.cpp',
       'IndexedDBClientImpl.h',
       'InspectorClientImpl.cpp',
       'InspectorClientImpl.h',
-      'InspectorFrontendClientImpl.cpp',
-      'InspectorFrontendClientImpl.h',
       'LinkHighlight.cpp',
       'LinkHighlight.h',
       'LocalFileSystemClient.cpp',
       'LocalFileSystemClient.h',
       'MediaKeysClientImpl.cpp',
       'MediaKeysClientImpl.h',
       'MIDIClientProxy.cpp',
       'MIDIClientProxy.h',
       'NavigatorContentUtilsClientImpl.cpp',
       'NavigatorContentUtilsClientImpl.h',
@@ skipping 281 matching lines @@
       ['os_posix==1 and OS!="mac"',
         {
           'web_unittest_files': [
             'tests/LocaleICUTest.cpp',
           ],
         }
       ],
     ],
   },
 }