Convert mask types from uint32_t to enum type

This applies to the following types:

- audio_gain_mode_t;
- audio_flags_mask_t;
- audio_channel_representation_t;
- audio_channel_mask_t;
- audio_devices_t.

Enum types are distinct thus proper overloading on the type
is possible in C++. Also, assignments to enum types are
less prone to errors.

Bug: 169889714
Test: basic audio functionality
      m stagefright
      atest audiopolicy_tests
Change-Id: I42506484b1d0b0482618b7314fad4c8012a06fb4
diff --git a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
index c30f048..13e1933 100644
--- a/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
+++ b/media/libmediaplayerservice/nuplayer/NuPlayerRenderer.cpp
@@ -1928,11 +1928,12 @@
     int32_t numChannels;
     CHECK(format->findInt32("channel-count", &numChannels));
 
-    int32_t channelMask;
-    if (!format->findInt32("channel-mask", &channelMask)) {
-        // signal to the AudioSink to derive the mask from count.
-        channelMask = CHANNEL_MASK_USE_CHANNEL_ORDER;
-    }
+    int32_t rawChannelMask;
+    audio_channel_mask_t channelMask =
+            format->findInt32("channel-mask", &rawChannelMask) ?
+                    static_cast<audio_channel_mask_t>(rawChannelMask)
+                    // signal to the AudioSink to derive the mask from count.
+                    : CHANNEL_MASK_USE_CHANNEL_ORDER;
 
     int32_t sampleRate;
     CHECK(format->findInt32("sample-rate", &sampleRate));