Revert 161821 "Remove 'FAST_MOBILE_SCROLLING'"

Source/build/features.gypi

 #
 # Copyright (C) 2009 Google Inc. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #
 #     * Redistributions of source code must retain the above copyright
 # notice, this list of conditions and the following disclaimer.
 #     * Redistributions in binary form must reproduce the above
@@ skipping 36 matching lines @@
       'enable_oilpan%': 0,
       'enable_touch_icon_loading%' : 0,
     },
     'conditions': [
       ['use_concatenated_impulse_responses==1', {
         # Use concatenated HRTF impulse responses
         'feature_defines': ['WTF_USE_CONCATENATED_IMPULSE_RESPONSES=1'],
       }],
       ['OS=="android"', {
         'feature_defines': [
+          'ENABLE_FAST_MOBILE_SCROLLING=1',
           'ENABLE_INPUT_SPEECH=0',
           'ENABLE_LEGACY_NOTIFICATIONS=0',
           'ENABLE_MEDIA_CAPTURE=1',
           'ENABLE_ORIENTATION_EVENTS=1',
           'ENABLE_TOUCH_ICON_LOADING=1',
           'ENABLE_NAVIGATOR_CONTENT_UTILS=0',
         ],
       }, { # OS!="android"
         'feature_defines': [
           'ENABLE_INPUT_SPEECH=1',
@@ skipping 30 matching lines @@
         ],
       }],
       ['enable_oilpan==1', {
         'feature_defines': [
           'ENABLE_OILPAN=1',
         ],
       }],
     ],
   },
 }