Turn on presentation feedback for Linux

Bug: 776877
Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: I9d9590a5174db94392a447ab280e9218b37c2958
Reviewed-on: https://chromium-review.googlesource.com/1040725Reviewed-by: Antoine Labour <piman@chromium.org>
Commit-Queue: Peng Huang <penghuang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#555782}

ui/gl/gl_switches_util.cc

@@ -13,7 +13,7 @@ namespace gl {
 
 bool IsPresentationCallbackEnabled() {
 // TODO(peng): always enable once 776877 is fixed.
-#if defined(OS_CHROMEOS) || defined(OS_ANDROID)
+#if defined(OS_CHROMEOS) || defined(OS_ANDROID) || defined(OS_LINUX)
   return true;
 #else
   return base::CommandLine::ForCurrentProcess()->HasSwitch(