More build config cleanup.

build/config/BUILD.gn

Index: build/config/BUILD.gn
diff --git a/build/config/BUILD.gn b/build/config/BUILD.gn
index 7759e59632baaf05a9e55cc9cfa44bfae9413c4b..f608ff2cd9c6ed66ea40235c87073c84a1f62131 100644
--- a/build/config/BUILD.gn
+++ b/build/config/BUILD.gn
@@ -61,18 +61,9 @@ config("feature_flags") {
     # TODO(brettw) should probably be "=1".
     defines += [ "UI_COMPOSITOR_IMAGE_TRANSPORT" ]
   }
-  if (use_ash) {
-    defines += [ "USE_ASH=1" ]
-  }
   if (use_aura) {
     defines += [ "USE_AURA=1" ]
   }
-  if (use_pango) {
-    defines += [ "USE_PANGO=1" ]
-  }
-  if (use_cairo) {
-    defines += [ "USE_CAIRO=1" ]
-  }
   if (use_openssl) {
     defines += [ "USE_OPENSSL=1" ]
   }