Refactor skia_warnings_as_errors

gyp/libjpeg.gyp

Index: gyp/libjpeg.gyp
===================================================================
--- gyp/libjpeg.gyp	(revision 8270)
+++ gyp/libjpeg.gyp	(working copy)
@@ -95,24 +95,36 @@
                 ],
               },
               'conditions': [
-                ['OS!="win"', {
+                [ 'skia_os != "win"', {
                   'product_name': 'jpeg',
                   'cflags': [
                    '-Wno-main', # supresses warnings about naming things "main"
                   ],
                 }],
-                ['OS=="android"', {
-                  'cflags!': [
-                   '-fno-rtti', # supresses warnings about invalid option of non-C++ code
-                   '-Wall',
-                   '-Werror',
+                # Turn off warnings as errors.
+                [ 'skia_warnings_as_errors', {
+                  'conditions': [
+                    [ 'skia_os == "mac" or skia_os == "ios"', {
+                      'xcode_settings': {
+                        'OTHER_CPLUSPLUSFLAGS!': [
+                          '-Werror',
+                        ]
+                      },
+                    }],
+                    [ 'skia_os == "win"', {
+                      'msvs_settings': {
+                        'VCCLCompilerTool': {
+                          'WarnAsError': 'false',
+                        },
+                      },
+                    }],
+                    [ 'skia_os in ["linux", "freebsd", "openbsd", "solaris", "nacl"]', {
+                      'cflags!': [
+                        '-Werror',
+                      ],
+                    }],
                   ],
                 }],
-                ['OS in ["linux", "freebsd", "openbsd", "solaris", "nacl"]', {
-                  'cflags!': [
-                   '-Werror',
-                  ],
-                }],
               ],
             },
           ],