Wire up SDL on mac

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)',
@@ skipping 370 matching lines @@
       # specifically requested. These should be temporary staging defines. Any
       # permanent defines should be moved into the skia_android_framework block
       # above.
       'includes' : [
         'skia_for_android_framework_defines.gypi',
       ],
       'defines': [
         '<@(skia_for_android_framework_defines)',
       ],
     }],
+    
+    [ 'skia_use_sdl == 1',
+      {
+        'defines': [ 'SK_USE_SDL' ],
+    }],
 
     [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "chromeos"]',
       {
         'defines': [
           'SK_SAMPLES_FOR_X',
           'SK_BUILD_FOR_UNIX',
         ],
         'configurations': {
           'Coverage': {
             'conditions': [
@@ skipping 231 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',
   },
 }