Add GetProcAddress to OpenGL control interface

R=jamesr@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1354353002 .
diff --git a/mojo/BUILD.gn b/mojo/BUILD.gn
index f83617f..b016b74 100644
--- a/mojo/BUILD.gn
+++ b/mojo/BUILD.gn
@@ -58,6 +58,7 @@
     "//mojo/services/view_manager/public/cpp/tests:mojo_view_manager_lib_unittests",
     "//mojo/tests:mojo_task_tracker_perftests",
     "//mojo/tools:message_generator",
+    "//mojo/gles2:mgl_unittests",
     "//mojo/gpu:apptests",
     "//mojo/services/files/public/c:apptests",
   ]