Add OzoneGLImpl interface.

ui/gl/BUILD.gn

Index: ui/gl/BUILD.gn
diff --git a/ui/gl/BUILD.gn b/ui/gl/BUILD.gn
index 8f9896b54cde15ba62750257c21b0a3fe57ec56d..bc11394c49c611517446fc22cd23338a1a858942 100644
--- a/ui/gl/BUILD.gn
+++ b/ui/gl/BUILD.gn
@@ -311,6 +311,10 @@ static_library("test_support") {
     configs += [ "//build/config/linux:x11" ]
     deps += [ "//ui/platform_window/x11" ]
   }
+
+  if (use_ozone) {
+    deps += [ "//ui/ozone" ]

[rjkroege, 2016/08/26 19:55:53]

Would it be too hard to narrow the dependency?. Can we only depend on
ui/ozone/public here?

[kylechar, 2016/08/29 15:38:14]

Well, the DEPS only allows ui/ozone/public for #include statements. There is no
//ui/ozone/public target but the //ui/ozone target only exposes headers in
//ui/ozone/public so it's essentially equivalent? 

This is also only to perform the GPU initialization for tests and might not be
necessary if that was done differently.

+  }
 }
 
 source_set("run_all_unittests") {