[Chromecast] Use cast ozone platforms for audio builds

This eliminates need for disable_display logic in a few places:
* logic for when to build Cast Ozone
* logic for --ozone-platform switches

Cast Ozone recently had headless mode added based on --disable-gpu
switch.  Rather than require all audio builds, tests etc to use this
switch, just enable headless mode for DISABLE_DISPLAY builds.

BUG=internal b/27268814

Review URL: https://codereview.chromium.org/1739353002

Cr-Commit-Position: refs/heads/master@{#379413}

1 files changed, 11 insertions, 15 deletions

diff --git a/ui/ozone/ozone.gni b/ui/ozone/ozone.gni
index 31e6dbf..2287c1e 100644
--- a/ui/ozone/ozone.gni
+++ b/ui/ozone/ozone.gni
@@ -37,22 +37,18 @@ declare_args() {
     ozone_platform_headless = true
 
     if (is_chromecast) {
-      if (!disable_display) {
-        # Enable the Cast ozone platform on all A/V Cast builds.
-        ozone_platform_cast = true
+      # Enable the Cast ozone platform on all A/V Cast builds.
+      ozone_platform_cast = true
 
-        # For desktop Chromecast builds, override the default "headless"
-        # platform with --ozone-platform=egltest
-        # TODO(halliwell): Create a libcast_graphics implementation for desktop
-        # using X11, and disable these two platforms. "cast" platform should be
-        # the default on every A/V build.
-        if (is_cast_desktop_build) {
-          ozone_platform_egltest = true
-          ozone_platform_ozonex = true
-        } else {
-          # On device builds, enable "cast" as the default platform.
-          ozone_platform = "cast"
-        }
+      # For visual desktop Chromecast builds, override the default "headless"
+      # platform with --ozone-platform=egltest
+      # TODO(halliwell): Create a libcast_graphics implementation for desktop
+      # using X11, and disable these two platforms.
+      if (is_cast_desktop_build && !disable_display) {
+        ozone_platform_egltest = true
+        ozone_platform_ozonex = true
+      } else {
+        ozone_platform = "cast"
       }
     } else if (is_chromeos) {
       ozone_platform_gbm = true