Refactor skia_warnings_as_errors

gyp/utils.gyp

 {
   'targets': [
     {
       'target_name': 'utils',
       'product_name': 'skia_utils',
       'type': 'static_library',
       'standalone_static_library': 1,
       'dependencies': [
         'cityhash',
       ],
@@ skipping 220 matching lines @@
       ],
       'sources': [
         '../third_party/externals/cityhash/src/city.cc',
       ],
       'direct_dependent_settings': {
         'include_dirs': [
           '../third_party/externals/cityhash/src',
         ],
       },
       'conditions': [
-        [ 'skia_os == "mac"', {
-          'xcode_settings': {
-            'OTHER_CPLUSPLUSFLAGS!': [
-              '-Werror',
-            ]
-          },
-        }],
-        [ 'skia_os == "win"', {
-          'msvs_settings': {
-            'VCCLCompilerTool': {
-              'WarnAsError': 'false',
-            },
-          },
-        }],
         [ 'skia_os == "android"', {
           'cflags!': [
             '-Wall',
-            '-Werror',
           ],
         }],
-        ['skia_os in ["linux", "freebsd", "openbsd", "solaris", "nacl"]', {
-          'cflags!': [
-            '-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", "android"]', {
+              'cflags!': [
+                '-Werror',
+              ],
+            }],
           ],
         }],
       ],
     },
   ],
 }
 
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