Refactor skia_warnings_as_errors

gyp/libjpeg.gyp

Index: gyp/libjpeg.gyp
===================================================================
--- gyp/libjpeg.gyp	(revision 8147)
+++ gyp/libjpeg.gyp	(working copy)
@@ -80,22 +80,40 @@
             ],
           },
           'conditions': [
-            ['OS!="win"', {
+            [ 'skia_os != "win"', {
               'product_name': 'jpeg',
               'cflags': [
                '-Wno-main', # supresses warnings about naming things "main"
               ],
             }],
-            ['OS=="android"', {
+            [ 'skia_os == "android"', {
               'cflags!': [
                '-fno-rtti', # supresses warnings about invalid option of non-C++ code
                '-Wall',
-               '-Werror',
               ],
             }],
-            ['OS in ["linux", "freebsd", "openbsd", "solaris", "nacl"]', {
-              'cflags!': [
-               '-Werror',
+            # Turn off warnings as errors.
+            [ 'skia_warnings_as_errors', {
+              'conditions': [
+                [ 'skia_os == "mac"', {
+                  'xcode_settings': {
+                    'OTHER_CPLUSPLUSFLAGS!': [
+                      '-Werror',
+                    ]
+                  },
+                }],
+                [ 'skia_os == "win"', {
+                  'msvs_settings': {
+                    'VCCLCompilerTool': {
+                      'WarnAsError': 'false',
+                    },
+                  },
+                }],
+                [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "nacl", "android"]', {
+                  'cflags!': [
+                    '-Werror',
+                  ],
+                }],
               ],
             }],
           ],