When was SkPDiff last used?

gyp/common_conditions.gypi

 # Copyright 2015 Google Inc.
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # conditions used in both common.gypi and skia.gyp in chromium
 #
 {
   'defines': [
     'SK_ALLOW_STATIC_GLOBAL_INITIALIZERS=<(skia_static_initializers)',
     'SK_SUPPORT_GPU=<(skia_gpu)',
-    'SK_SUPPORT_OPENCL=<(skia_opencl)',
     'SK_FORCE_DISTANCE_FIELD_TEXT=<(skia_force_distance_field_text)',
   ],
   'conditions' : [
     ['skia_pic', {
      'cflags': [
        '-fPIC',
      ],
      'conditions' : [
       # FIXME: The reason we don't do this on Android is due to the way
       # we build the executables/skia_launcher on Android. See
@@ skipping 624 matching lines @@
           'LD_RUNPATH_SEARCH_PATHS': ['@executable_path/.'],
       },
     }],
 
   ], # end 'conditions'
   # The Xcode SYMROOT must be at the root. See build/common.gypi in chromium for more details
   'xcode_settings': {
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }