Remove unusued WebFrameClient::willRequestResource and WebCachedURLRequest

Source/web/web.gypi

 {
   'variables': {
     'web_files': [
       'AssertMatchingEnums.cpp',
       'AssociatedURLLoader.cpp',
       'AssociatedURLLoader.h',
       'ChromeClientImpl.cpp',
       'ChromeClientImpl.h',
       'ColorChooserPopupUIController.cpp',
       'ColorChooserPopupUIController.h',
@@ skipping 93 matching lines @@
       'ValidationMessageClientImpl.cpp',
       'ValidationMessageClientImpl.h',
       'ViewportAnchor.h',
       'WebAXObject.cpp',
       'WebArrayBuffer.cpp',
       'WebArrayBufferConverter.cpp',
       'WebArrayBufferView.cpp',
       'WebBindings.cpp',
       'WebBlob.cpp',
       'WebCache.cpp',
-      'WebCachedURLRequest.cpp',
       'WebColorName.cpp',
       'WebColorSuggestion.cpp',
       'WebCryptoNormalize.cpp',
       'WebCustomElement.cpp',
       'WebCSSParser.cpp',
       'WebDOMActivityLogger.cpp',
       'WebDOMCustomEvent.cpp',
       'WebDOMError.cpp',
       'WebDOMEvent.cpp',
       'WebDOMFileSystem.cpp',
@@ skipping 198 matching lines @@
         {
           'web_unittest_files': [
             # Mac uses ScrollAnimatorMac instead of ScrollAnimatorNone.
             'tests/ScrollAnimatorNoneTest.cpp',
           ],
         }
       ],
     ],
   },
 }