Rename ENABLE(DEFAULT_RENDER_THEME) to USE(DEFAULT_RENDER_THEME).

Source/core/features.gypi

Index: Source/core/features.gypi
diff --git a/Source/core/features.gypi b/Source/core/features.gypi
index e5d8d6b0364d8a9006f39eb46a8ed810f5efeee6..a4a2764e14da6bb5873578909c5b33563c25f5e2 100644
--- a/Source/core/features.gypi
+++ b/Source/core/features.gypi
@@ -102,11 +102,6 @@
           'ENABLE_RUBBER_BANDING=1',
         ],
       }],
-      ['use_default_render_theme==1', {
-        'feature_defines': [
-          'ENABLE_DEFAULT_RENDER_THEME=1',
-        ],
-      }],
     ],
   },
 }