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/libaudiofoundation/AudioGain.cpp b/media/libaudiofoundation/AudioGain.cpp
index 0d28335..759140e 100644
--- a/media/libaudiofoundation/AudioGain.cpp
+++ b/media/libaudiofoundation/AudioGain.cpp
@@ -152,8 +152,12 @@
     if ((status = parcel->readInt32(&mIndex)) != NO_ERROR) return status;
     if ((status = parcel->readBool(&mUseInChannelMask)) != NO_ERROR) return status;
     if ((status = parcel->readBool(&mUseForVolume)) != NO_ERROR) return status;
-    if ((status = parcel->readUint32(&mGain.mode)) != NO_ERROR) return status;
-    if ((status = parcel->readUint32(&mGain.channel_mask)) != NO_ERROR) return status;
+    uint32_t rawGainMode;
+    if ((status = parcel->readUint32(&rawGainMode)) != NO_ERROR) return status;
+    mGain.mode = static_cast<audio_gain_mode_t>(rawGainMode);
+    uint32_t rawChannelMask;
+    if ((status = parcel->readUint32(&rawChannelMask)) != NO_ERROR) return status;
+    mGain.channel_mask = static_cast<audio_channel_mask_t>(rawChannelMask);
     if ((status = parcel->readInt32(&mGain.min_value)) != NO_ERROR) return status;
     if ((status = parcel->readInt32(&mGain.max_value)) != NO_ERROR) return status;
     if ((status = parcel->readInt32(&mGain.default_value)) != NO_ERROR) return status;