Add GN build for parts of gpu and ozone.

ui/ozone/ozone.gni

+# Copyright 2014 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//build/config/ui.gni")
+
+if (use_ozone) {
+  # This is the default platform.
+  # TODO(GYP) presumably this needs to be settable, it's not clear to me how
+  # this is used.
+  ozone_platform = "test"

[spang, 2014/05/14 19:56:17]

It gets passed to generate_ozone_platform_list.py

That script just rearranges the list so that the default is first.

Then, if you do not specify the --ozone-platform flag, the first entry in the
list is used.

+
+  # Enable built-in ozone platforms if ozone is enabled.
+  ozone_platform_caca = false
+  ozone_platform_dri = true
+  ozone_platform_ozonex = false
+  ozone_platform_test = true
+} else {
+  ozone_platform_caca = false
+  ozone_platform_dri = false
+  ozone_platform_ozonex = false
+  ozone_platform_test = false
+}