Add Ozone configuration to facilitate management of external platforms

ui/ozone/BUILD.gn

 # 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")
 import("//ui/ozone/ozone.gni")
+import("//ui/ozone/ozone_extra.gni")
 import("//testing/test.gni")
 
 assert(use_ozone)
 
 visibility = [ ":*" ]
 
 # The list of platforms that will be built.
-ozone_platforms = []
+ozone_platforms = ozone_external_platforms

[rjkroege, 2016/10/31 20:41:46]

Can you test this with a simple-chrome ChromeOS build before landing?

[fwang, 2016/10/31 20:56:05]

OK, I have not tested caca on ChromeOS because software rendering is not allowed
but I can try it using
https://groups.google.com/a/chromium.org/group/ozone-dev/attach/4a886fa59b97b...

 
 # Extra dependencies to pull into ui/ozone for built platforms.
-ozone_platform_deps = []
+ozone_platform_deps = ozone_external_platform_deps
 
 # Extra dependencies to pull into ozone_unittests for built platforms.
-ozone_platform_test_deps = []
+ozone_platform_test_deps = ozone_external_platform_test_deps
 
 if (ozone_platform_headless) {
   ozone_platforms += [ "headless" ]
   ozone_platform_deps += [ "platform/headless" ]
 }
 
 if (ozone_platform_gbm) {
   ozone_platforms += [ "gbm" ]
   ozone_platform_deps += [ "platform/drm:gbm" ]
   ozone_platform_test_deps += [ "platform/drm:gbm_unittests" ]
@@ skipping 191 matching lines @@
     "//ui/gfx/geometry",
   ]
 
   # Add tests of platform internals.
   deps += ozone_platform_test_deps
 
   # Platform tests link ozone statically. Make sure we're not getting a
   # 2nd copy of any code via the component.
   assert_no_deps = [ "//ui/ozone" ]
 }