[Chromecast] Enable CMA by default on Android.

This allows some Java code to be compiled on CQ that wasn't
previously.

Bug: None
Test: build cast_shell_apk
Change-Id: Icaa97f7fef8a805942355aac14634a270bff57e3
Reviewed-on: https://chromium-review.googlesource.com/1241847Reviewed-by: Frank Liberato <liberato@chromium.org>
Reviewed-by: Luke Halliwell <halliwell@chromium.org>
Commit-Queue: Simeon Anfinrud <sanfin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#594451}

chromecast/media/cma/backend/android/java/src/org/chromium/chromecast/cma/backend/android/AudioSinkAudioTrackImpl.java

@@ -121,7 +121,7 @@ class AudioSinkAudioTrackImpl {
     // Additional padding for minimum buffer time, determined experimentally.
     private static final long MIN_BUFFERED_TIME_PADDING_US = ANDROID_AUDIO_PERIOD_SIZE_US;
 
-    private static AudioManager sAudioManager = null;
+    private static AudioManager sAudioManager;
 
     private static int sSessionIdMedia = AudioManager.ERROR;
     private static int sSessionIdCommunication = AudioManager.ERROR;

chromecast/media/cma/backend/android/java/src/org/chromium/chromecast/cma/backend/android/VolumeControl.java

@@ -45,7 +45,7 @@ class VolumeControl {
         Settings(int streamType) {
             mStreamType = streamType;
             mMaxVolumeIndexAsFloat = (float) mAudioManager.getStreamMaxVolume(mStreamType);
-            mMinVolumeIndex = mAudioManager.getStreamMinVolume(mStreamType);
+            mMinVolumeIndex = getStreamMinVolume(mAudioManager, mStreamType);
             refreshVolume();
             refreshMuteState();
         }
@@ -261,6 +261,14 @@ class VolumeControl {
         mSettings.get(castType).setMuted(muted);
     }
 
+    @SuppressWarnings("NewApi")
+    private static int getStreamMinVolume(AudioManager audioManager, int streamType) {
+        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.P) {
+            return audioManager.getStreamMinVolume(streamType);
+        }
+        return 0;
+    }
+
     //
     // JNI functions in native land.
     //

media/media_options.gni

@@ -77,7 +77,8 @@ declare_args() {
   enable_hls_sample_aes = proprietary_codecs && is_chromecast
 
   # If true, use cast CMA backend instead of default chromium media pipeline.
-  is_cast_using_cma_backend = is_cast_audio_only || !is_android
+  # TODO(sanfin): Remove this flag when all builds enable CMA.
+  is_cast_using_cma_backend = true
 }
 
 # enable_hls_sample_aes can only be true if enable_mse_mpeg2ts_stream_parser is.