Added switch to disable specified GL extensions.

ui/gfx/BUILD.gn

Index: ui/gfx/BUILD.gn
diff --git a/ui/gfx/BUILD.gn b/ui/gfx/BUILD.gn
index 43a7d7aa360cd2fa0e61d42227c722f05986846c..ef148854e5f65a118b2df5d0f52b86743c5290f5 100644
--- a/ui/gfx/BUILD.gn
+++ b/ui/gfx/BUILD.gn
@@ -242,6 +242,7 @@ component("gfx") {
     "//third_party/libpng",
     "//third_party/zlib",
     "//ui/gfx/geometry",
+    "//ui/gl",
   ]
   public_deps = [
     "//base",
@@ -394,6 +395,7 @@ source_set("test_support") {
 
 test("gfx_unittests") {
   sources = [
+    "//ui/gl/gl_api_unittest.cc",

[no sievers, 2015/05/01 21:55:00]

nit: maybe we can also treat these ui/gl unittest sources as a different set
here?

[David Yen, 2015/05/01 22:34:38]

GN has much stricter gfx -> gl dependency rules so I am not sure if it is
possible... I just removed this change.

     "font_render_params_linux_unittest.cc",
     "font_unittest.cc",
     "image/image_family_unittest.cc",
@@ -473,6 +475,7 @@ test("gfx_unittests") {
     "//testing/gtest",
     "//ui/base",
     "//ui/gfx/geometry",
+    "//ui/gl",
     "//ui/resources:ui_test_pak",
   ]