add show_about_flag_aura_window_mode in common.gypi

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index bc6b71bb715788b15071d13364961839b434184b..0aade787c75ac9a73a580361eb214a95e44e32a0 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -45,9 +45,15 @@
           # Default setting for use_skia on mac platform.
           # This is typically overridden in use_skia_on_mac.gypi.
           'use_skia_on_mac%': 0,
+
+          # Whether or not to show the aura-window-mode flag in about://flags.
+          # TODO(alicet): Remove this when we can expose the flag to
+          # all chromeos platforms.
+          'aura_show_about_flag_window_mode': 0,
         },
         # Copy conditionally-set variables out one scope.
         'chromeos%': '<(chromeos)',
+        'aura_show_about_flag_window_mode%': '<(aura_show_about_flag_window_mode)',
         'views_compositor%': '<(views_compositor)',
         'use_aura%': '<(use_aura)',
         'use_ash%': '<(use_ash)',
@@ -72,6 +78,11 @@
             'use_aura%': 1,
           }],
 
+          # show aura-window-mode about flag by default.
+          ['use_aura==1', {
+            'aura_show_about_flag_window_mode': 1,
+          }],
+
           # Set default value of toolkit_views based on OS.
           ['OS=="win" or chromeos==1 or use_aura==1', {
             'toolkit_views%': 1,
@@ -96,6 +107,7 @@
       # Copy conditionally-set variables out one scope.
       'chromeos%': '<(chromeos)',
       'host_arch%': '<(host_arch)',
+      'aura_show_about_flag_window_mode%': '<(aura_show_about_flag_window_mode)',
       'toolkit_views%': '<(toolkit_views)',
       'views_compositor%': '<(views_compositor)',
       'use_webkit_compositor%': '<(use_webkit_compositor)',
@@ -362,6 +374,7 @@
     'target_arch%': '<(target_arch)',
     'host_arch%': '<(host_arch)',
     'library%': 'static_library',
+    'aura_show_about_flag_window_mode%': '<(aura_show_about_flag_window_mode)',
     'toolkit_views%': '<(toolkit_views)',
     'views_compositor%': '<(views_compositor)',
     'ui_compositor_image_transport%': '<(ui_compositor_image_transport)',
@@ -840,6 +853,9 @@
       ['chromeos==1', {
         'grit_defines': ['-D', 'chromeos'],
       }],
+      ['aura_show_about_flag_window_mode==1', {
+        'grit_defines': ['-D', 'aura_show_about_flag_window_mode'],
+      }],
       ['toolkit_views==1', {
         'grit_defines': ['-D', 'toolkit_views'],
       }],
@@ -1008,6 +1024,9 @@
         # See http://code.google.com/p/chromium/issues/detail?id=98755 .
         'defines': ['COMPILE_CONTENT_STATICALLY'],
       }],
+      ['aura_show_about_flag_window_mode==1', {
+        'defines': ['AURA_SHOW_ABOUT_FLAG_WINDOW_MODE=1'],
+      }],
       ['toolkit_views==1', {
         'defines': ['TOOLKIT_VIEWS=1'],
       }],