Enable HiDPI assets for the WebUI in iOS.

build/common.gypi

 # Copyright (c) 2012 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.
 
 # IMPORTANT:
 # Please don't directly include this file if you are building via gyp_chromium,
 # since gyp_chromium is automatically forcing its inclusion.
 {
   # Variables expected to be overriden on the GYP command line (-D) or by
   # ~/.gyp/include.gypi.
@@ skipping 1521 matching lines @@
       }],
       ['OS=="android"', {
         'grit_defines': ['-t', 'android',
                          '-E', 'ANDROID_JAVA_TAGGED_ONLY=true'],
         'conditions': [
           ['google_tv==1', {
             'grit_defines': ['-D', 'google_tv'],
           }],
         ],
       }],
-      ['OS=="mac"', {
+      ['OS=="mac" or OS=="ios"', {
         'grit_defines': ['-D', 'scale_factors=2x'],
       }],
       ['OS == "ios"', {
         'grit_defines': [
           # define for iOS specific resources.
           '-D', 'ios',
           # iOS uses a whitelist to filter resources.
           '-w', '<(DEPTH)/build/ios/grit_whitelist.txt'
         ],
 
@@ skipping 3085 matching lines @@
     # settings in target dicts.  SYMROOT is a special case, because many other
     # Xcode variables depend on it, including variables such as
     # PROJECT_DERIVED_FILE_DIR.  When a source group corresponding to something
     # like PROJECT_DERIVED_FILE_DIR is added to a project, in order for the
     # files to appear (when present) in the UI as actual files and not red
     # red "missing file" proxies, the correct path to PROJECT_DERIVED_FILE_DIR,
     # and therefore SYMROOT, needs to be set at the project level.
     'SYMROOT': '<(DEPTH)/xcodebuild',
   },
 }