linux_aura: Turn aura on on the builders.

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,
             }],
 
+            # ToT Linux should be aura.
+            #
+            # TODO(erg): Merge this into the previous block once compiling with
+            # aura safely implies including ash capabilities.
+            ['OS=="linux"', {
+              '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,
             }],
 
@@ skipping 4654 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',
   },
 }