When was SkPDiff last used?

gyp/common_variables.gypi

 # Copyright 2012 The Android Open Source Project
 #
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 {
   # Get ready for the ugly...
   #
   # - We have to nest our variables dictionaries multiple levels deep, so that
   #   this and other gyp files can rely on previously-set variable values in
@@ skipping 124 matching lines @@
       'skia_angle%': 0,
       'skia_command_buffer%': 0,
       'skia_gdi%': 0,
       'skia_gpu%': 1,
       'skia_osx_deployment_target%': '',
       'skia_pdf%': 1,
       'skia_profile_enabled%': 0,
       'skia_vulkan%': 0,
       'skia_win_debuggers_path%': '',
       'skia_shared_lib%': 0,
-      'skia_opencl%': 0,
       'skia_force_distance_field_text%': 0,
       'skia_is_bot%': '<!(python -c "import os; print os.environ.get(\'CHROME_HEADLESS\', 0)")',
 
       # These variables determine the default optimization level for different
       # compilers.
       'skia_default_vs_optimization_level': 3, # full (/Ox)
       'skia_default_gcc_optimization_level': 3, # -O3
     },
 
     'conditions': [
@@ skipping 64 matching lines @@
     'skia_gdi%': '<(skia_gdi)',
     'skia_gpu%': '<(skia_gpu)',
     'skia_vulkan%': '<(skia_vulkan)',
     'skia_win_exceptions%': 0,
     'skia_win_ltcg%': '<(skia_is_bot)',
     'skia_osx_deployment_target%': '<(skia_osx_deployment_target)',
     'skia_pdf%': '<(skia_pdf)',
     'skia_pdf_generate_pdfa%': 0,  # emit larger PDF/A-2b file
     'skia_profile_enabled%': '<(skia_profile_enabled)',
     'skia_shared_lib%': '<(skia_shared_lib)',
-    'skia_opencl%': '<(skia_opencl)',
     'skia_force_distance_field_text%': '<(skia_force_distance_field_text)',
     'skia_static_initializers%': '<(skia_static_initializers)',
     'ios_sdk_version%': '6.0',
     'skia_win_debuggers_path%': '<(skia_win_debuggers_path)',
     'skia_disable_inlining%': 0,
     'skia_moz2d%': 0,
     'skia_is_bot%': '<(skia_is_bot)',
     'skia_egl%': '<(skia_egl)',
     'skia_use_sdl%': 0,
     'skia_fast%': 0,
     'skia_dump_stats%': 0,
     'skia_fast_flags': [
         '-O3',                   # Even for Debug builds.
         '-march=native',         # Use all features of and optimize for THIS machine.
         '-fomit-frame-pointer',  # Sometimes an extra register is nice, and cuts a push/pop.
         '-ffast-math',           # Optimize float math even when it breaks IEEE compliance.
         #'-flto'                  # Enable link-time optimization.
     ],
 
     # These are referenced by our .gypi files that list files (e.g. core.gypi)
     #
     'skia_src_path%': '../src',
     'skia_include_path%': '../include',
   },
 }