[Chromecast] Audio-only builds should not enable "cast" ozone platform.

Currently this is being configured in infrastructure. Remove the
complexity of setting up an audio build by setting the "headless"
platform to default for "disable_display" builds.

BUG=

Review URL: https://codereview.chromium.org/1442643005

Cr-Commit-Position: refs/heads/master@{#359578}

1 files changed, 14 insertions, 9 deletions

diff --git a/ui/ozone/ozone.gni b/ui/ozone/ozone.gni
index 15e909d..a1fe2f8 100644
--- a/ui/ozone/ozone.gni
+++ b/ui/ozone/ozone.gni
@@ -30,16 +30,21 @@ declare_args() {
 
   if (ozone_auto_platforms) {
     if (is_chromecast) {
-      # The default platform used at runtime is "cast".
-      ozone_platform = "cast"
-      ozone_platform_cast = true
       ozone_platform_headless = true
-
-      # For desktop Chromecast builds, override the default "cast" platform with
-      # --ozone_platform=egltest
-      if (target_os == "linux" && target_cpu != "arm") {
-        ozone_platform_egltest = true
-        ozone_platform_ozonex = true
+      if (disable_display) {
+        # Audio-only builds should use the "headless" platform by default.
+        ozone_platform = "headless"
+      } else {
+        # Builds with video should default to the "cast" platform.
+        ozone_platform_cast = true
+        ozone_platform = "cast"
+
+        # For desktop Chromecast builds, override the default "cast" platform with
+        # --ozone_platform=egltest
+        if (target_os == "linux" && target_cpu != "arm") {
+          ozone_platform_egltest = true
+          ozone_platform_ozonex = true
+        }
       }
     } else {
       # Use headless as the default platform.