Add gyp support for new GPU backend

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 114 matching lines @@
       'skia_gpu_extra_dependency_path%': '',
       'skia_stroke_path_rendering%': 0,
       'skia_android_path_rendering%': 0,
       'skia_resource_cache_mb_limit%': 0,
       'skia_resource_cache_count_limit%': 0,
       'skia_angle%': 0,
       'skia_gdi%': 0,
       'skia_gpu%': 1,
       'skia_osx_deployment_target%': '',
       'skia_profile_enabled%': 0,
+      'skia_vulkan%': 0,
       'skia_win_debuggers_path%': '',
       'skia_shared_lib%': 0,
       'skia_opencl%': 0,
       'skia_force_distance_field_text%': 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
     },
@@ skipping 52 matching lines @@
     'skia_use_android_framework_defines%': '<(skia_use_android_framework_defines)',
     'skia_use_system_json%': '<(skia_use_system_json)',
     'skia_android_path_rendering%': '<(skia_android_path_rendering)',
     'skia_resource_cache_mb_limit%': '<(skia_resource_cache_mb_limit)',
     'skia_resource_cache_count_limit%': '<(skia_resource_cache_count_limit)',
     'skia_angle%': '<(skia_angle)',
     'skia_arch_type%': '<(skia_arch_type)',
     'skia_chrome_utils%': '<(skia_chrome_utils)',
     'skia_gdi%': '<(skia_gdi)',
     'skia_gpu%': '<(skia_gpu)',
+    'skia_vulkan%': '<(skia_vulkan)',
     'skia_win_exceptions%': 0,
     'skia_win_ltcg%': 1,
     'sknx_no_simd%': 0,
     'skia_osx_deployment_target%': '<(skia_osx_deployment_target)',
     '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',
@@ skipping 11 matching lines @@
         '-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',
   },
 }