Make ChromeOS imply enable_hidpi

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 107 matching lines @@
             'toolkit_views%': 0,
           }],
 
           # Set toolkit_uses_gtk for the Chromium browser on Linux.
           ['(OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris") and use_aura==0', {
             'toolkit_uses_gtk%': 1,
           }, {
             'toolkit_uses_gtk%': 0,
           }],
 
-          # Enable HiDPI on Mac OS.
-          ['OS=="mac"', {
+          # Enable HiDPI on Mac OS and Chrome OS.
+          ['OS=="mac" or chromeos==1', {
             'enable_hidpi%': 1,
           }],
 
           # Enable touch UI on Metro and Chrome OS.
           ['OS=="win" or chromeos==1', {
             'enable_touch_ui%': 1,
           }],
         ],
       },
 
@@ skipping 3242 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',
   },
 }