Ensure cast on Android does not use MojoRenderer

We need to enable CMA on some Android devices, but we should continue
using MojoAudioDecoder and MojoVideoDecoder in the gpu process. This
affects Android-based Cast devices.

BUG=b:111465269
TEST=Build, cast YT

Change-Id: Ic76d695204720b91d99ab53ae3b40513cea962c5
Reviewed-on: https://chromium-review.googlesource.com/1139103
Commit-Queue: Aidan Wolter <awolter@chromium.org>
Reviewed-by: Thomas Guilbert <tguilbert@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576315}

media/media_options.gni

@@ -177,14 +177,14 @@ _default_mojo_media_host = "none"
 # Can be overridden by gn build arguments from the --args command line flag
 # for local testing.
 if (enable_mojo_media) {
-  if (is_chromecast && is_cast_using_cma_backend) {
+  if (is_chromecast && is_cast_using_cma_backend && !is_android) {
     _default_mojo_media_services = [
       "cdm",
       "renderer",
     ]
     _default_mojo_media_host = "browser"
   } else if (is_android) {
-    # Both chrome for Android and cast for ATV belongs to this case
+    # Both chrome for Android and cast for Android belongs to this case
     _default_mojo_media_services = [
       "cdm",
       "audio_decoder",