Force use_ash to 0 if use_aura is 0.

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 57 matching lines @@
           # Override branding to select the desired branding flavor.
           'branding%': 'Chromium',
 
           'conditions': [
             # ChromeOS and Windows use Aura and Ash.
             ['chromeos==1 or OS=="win"', {
               'use_ash%': 1,
               'use_aura%': 1,
             }],
 
-            # For now, Windows builds that |use_aura| should also imply using
-            # ash. This rule should be removed for the future when Windows is
-            # using the aura windows without the ash interface.
-            ['use_aura==1 and OS=="win"', {
-              'use_ash%': 1,
-            }],
-            ['use_ash==1', {
-              'use_aura%': 1,
-            }],
-
             # Whether we're a traditional desktop unix.
             ['(OS=="linux" or OS=="freebsd" or OS=="openbsd" or OS=="solaris") and chromeos==0', {
               'desktop_linux%': 1,
             }, {
               'desktop_linux%': 0,
             }],
 
             # Compute the architecture that we're building on.
             ['OS=="win" or OS=="mac" or OS=="ios"', {
               'host_arch%': 'ia32',
@@ skipping 32 matching lines @@
         # build system.
         'android_webview_build%': 0,
 
         # Sets whether chrome is built for google tv device.
         'google_tv%': 0,
 
         # Set ARM architecture version.
         'arm_version%': 7,
 
         'conditions': [
+          # Ash needs Aura.

[gab, 2013/10/04 17:54:15]

So it actually looks like the first block above defines "default values" which
(unless overwritten by chromium.gyp_env) are copied to this block which is then
responsible for changing variables based on conditions based on other variables.

(and there seems to be more nested blocks of variables below... this is crazy...
but I think this works...!)

Having this code above would not work as use_aura is always 0 if not specified
(until it is defined by the default in the previous block which is only readable
here... gyp isn't sequential line-by-line, but rather block by block... it
appears...!

[scottmg, 2013/10/04 18:20:31]

Yeah, that's what I was trying to say before. Crazy indeed. lgtm2.

+          ['use_aura==0', {
+            'use_ash%': 0,
+          }],
+
           # Set default value of toolkit_views based on OS.
           ['OS=="win" or chromeos==1 or use_aura==1', {
             'toolkit_views%': 1,
           }, {
             'toolkit_views%': 0,
           }],
 
           # Set toolkit_uses_gtk for the Chromium browser on Linux.
           ['desktop_linux==1 and use_aura==0 and use_ozone==0', {
             'toolkit_uses_gtk%': 1,
@@ skipping 4592 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',
   },
 }