Refactor how clang warning flags are set.

skia/skia_chrome.gypi

 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 
 # This gypi file contains all the Chrome-specific enhancements to Skia.
 # In component mode (shared_lib) it is folded into a single shared library with
 # the Skia files but in all other cases it is a separate library.
 {
   'dependencies': [
     'skia_library',
     'skia_chrome_opts',
     '../base/base.gyp:base',
     '../base/third_party/dynamic_annotations/dynamic_annotations.gyp:dynamic_annotations',
   ],
 
   'direct_dependent_settings': {
     'include_dirs': [
       'ext',
     ],
   },
-
+  'variables': {
+    # TODO(scottmg): http://crbug.com/177306
+    'clang_warning_flags_unset': [
+      # Don't warn about string->bool used in asserts.
+      '-Wstring-conversion',
+    ],
+  },
   'sources': [
     # Note: file list duplicated in GN build.
     'ext/analysis_canvas.cc',
     'ext/analysis_canvas.h',
     'ext/benchmarking_canvas.cc',
     'ext/benchmarking_canvas.h',
     'ext/bitmap_platform_device.h',
     'ext/bitmap_platform_device_cairo.cc',
     'ext/bitmap_platform_device_cairo.h',
     'ext/bitmap_platform_device_mac.cc',
@@ skipping 59 matching lines @@
       ],
     }],
     ['OS == "ios"', {
       'sources/': [
         ['exclude', '^ext/vector_platform_device_skia\\.'],
       ],
       'dependencies!': [
         'skia_chrome_opts',
       ],
     }],
-    # TODO(scottmg): http://crbug.com/177306
-    ['clang==1', {
-      'xcode_settings': {
-        'WARNING_CFLAGS!': [
-          # Don't warn about string->bool used in asserts.
-          '-Wstring-conversion',
-        ],
-      },
-      'cflags!': [
-        '-Wstring-conversion',
-      ],
-    }],
     [ 'OS != "android" and (OS != "linux" or use_cairo==1)', {
       'sources!': [
         'ext/bitmap_platform_device_skia.cc',
       ],
     }],
   ],
 
   'target_conditions': [
     # Pull in specific linux files for android (which have been filtered out
     # by file name rules).
     [ 'OS == "android"', {
       'sources/': [
         ['include', 'ext/platform_device_linux\\.cc$'],
       ],
     }],
   ],
 }