login: Enable GLImage output for Pepper3D on kevin.

Makes it possible to use HW overlays for output.

BUG=chromium:680851
TEST=emerge-kevin chromeos-base/chromeos-login

Change-Id: I7c379d3311fdf81a68e6c05e0da43da80f1cba18
Reviewed-on: https://chromium-review.googlesource.com/428550
Commit-Ready: David Reveman <reveman@chromium.org>
Tested-by: David Reveman <reveman@chromium.org>
Reviewed-by: Dan Erat <derat@chromium.org>
diff --git a/login_manager/chrome_setup.cc b/login_manager/chrome_setup.cc
index 078fcdf..e73bb17 100644
--- a/login_manager/chrome_setup.cc
+++ b/login_manager/chrome_setup.cc
@@ -224,6 +224,7 @@
     builder->AddArg("--ash-enable-palette");
 
   if (builder->UseFlagIsSet("kevin")) {
+    builder->AddFeatureEnableOverride("Pepper3DImageChromium");
     // TODO(jdufault): Remove this once quick unlock launches on all boards.
     builder->AddFeatureEnableOverride("QuickUnlockPin");