Add --use-more-webui runtime flag to toggle WebUI replacements for native dialogs.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index f060eb5c25e32dc9f32ffb5296a27580523712bf..0134fd5fdeaf4dc2d97863e68d662b6f68aad3b2 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -34,11 +34,6 @@
           # Disable touch support by default.
           'touchui%': 0,
 
-          # Disable webui dialog replacements for native dialogs by default.
-          # TODO(flackr): Change this to a runtime flag triggered by
-          #     --pure-views so that these dialogs can be easily tested.
-          'webui_dialogs%': 0,
-
           # Whether the compositor is enabled on views.
           'views_compositor%': 0,
 
@@ -49,7 +44,6 @@
         'chromeos%': '<(chromeos)',
         'use_only_pure_views%': '<(use_only_pure_views)',
         'touchui%': '<(touchui)',
-        'webui_dialogs%': '<(webui_dialogs)',
         'views_compositor%': '<(views_compositor)',
         'use_aura%': '<(use_aura)',
 
@@ -80,11 +74,6 @@
             'use_only_pure_views%': 0,
           }],
 
-          # Use WebUI dialogs in TouchUI and PureView builds.
-          ['touchui==1 or use_only_pure_views==1 or use_aura==1', {
-            'webui_dialogs%': 1,
-          }],
-
           # Use the views compositor when using the Aura window manager.
           ['use_aura==1', {
             'views_compositor%': 1,
@@ -95,7 +84,6 @@
       # Copy conditionally-set variables out one scope.
       'chromeos%': '<(chromeos)',
       'touchui%': '<(touchui)',
-      'webui_dialogs%': '<(webui_dialogs)',
       'host_arch%': '<(host_arch)',
       'toolkit_views%': '<(toolkit_views)',
       'use_only_pure_views%': '<(use_only_pure_views)',
@@ -308,7 +296,6 @@
     'enable_flapper_hacks%': '<(enable_flapper_hacks)',
     'chromeos%': '<(chromeos)',
     'touchui%': '<(touchui)',
-    'webui_dialogs%': '<(webui_dialogs)',
     'file_manager_extension%': '<(file_manager_extension)',
     'webui_task_manager%': '<(webui_task_manager)',
     'inside_chromium_build%': '<(inside_chromium_build)',
@@ -671,9 +658,6 @@
       ['touchui==1', {
         'grit_defines': ['-D', 'touchui'],
       }],
-      ['webui_dialogs==1', {
-        'grit_defines': ['-D', 'webui_dialogs'],
-      }],
       ['file_manager_extension==1', {
         'grit_defines': ['-D', 'file_manager_extension'],
       }],