gn fixes for ui/gl and mac

third_party/mesa/BUILD.gn

Index: third_party/mesa/BUILD.gn
diff --git a/third_party/mesa/BUILD.gn b/third_party/mesa/BUILD.gn
new file mode 100644
index 0000000000000000000000000000000000000000..c0fe782b8a4e823ac73c674552ff739fb72e0120
--- /dev/null
+++ b/third_party/mesa/BUILD.gn
@@ -0,0 +1,16 @@
+# Copyright 2014 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.
+
+import("//build/config/ui.gni")
+
+config("mesa_headers_config") {
+  include_dirs = [ "src/include" ]
+  if (use_x11) {
+    defines = [ "MESA_EGL_NO_X11_HEADERS" ]
+  }
+}
+
+source_set("mesa_headers") {
+  direct_dependent_configs = [ ":mesa_headers_config" ]
+}