Add is_chromecast to GN build.

ui/ozone/ozone.gni

Index: ui/ozone/ozone.gni
diff --git a/ui/ozone/ozone.gni b/ui/ozone/ozone.gni
index e0da9196bd19159b67031bc26b6c3869a6d04dd8..a1183d26e9ba57ef93c9b50e5faf68c4904deba2 100644
--- a/ui/ozone/ozone.gni
+++ b/ui/ozone/ozone.gni
@@ -2,9 +2,11 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+import("//build/config/chromecast_build.gni")
+
 declare_args() {
   # Select platforms automatically. Turn this off for manual control.
-  ozone_auto_platforms = true
+  ozone_auto_platforms = !is_chromecast
 }
 
 declare_args() {
@@ -13,6 +15,7 @@ declare_args() {
 
   # Enable individual platforms.
   ozone_platform_caca = false
+  ozone_platform_cast = false
   ozone_platform_egltest = false
   ozone_platform_gbm = false
   ozone_platform_ozonex = false
@@ -27,5 +30,16 @@ declare_args() {
     ozone_platform_gbm = true
     ozone_platform_test = true
     ozone_platform_egltest = true
+  } else if (is_chromecast) {
+    # The default platform used at runtime is "cast".
+    ozone_platform = "cast"
+
+    # This platform is the default for all Chromecast builds.
+    ozone_platform_cast = true
+
+    # For desktop Chromecast builds, override the default "cast" platform with
+    # --ozone_platform=egltest
+    ozone_platform_egltest = true
+    ozone_platform_ozonex = true

[gunsch, 2015/09/16 04:41:48]

we also use ozone_platform_test (for our automated test running)

[slan, 2015/09/16 16:13:08]

Added.

   }
 }