Use channel mask instead of channel count for track creation

Record and playback objects (resp AudioRecord and AudioTrack)
are created using a channel mask, but this information is lost
in the mixer because only the channel count is known to
AudioFlinger. A channel count can always be derived from a
channel mask.

The change consists in:
- disambiguiting variable names for channel masks and counts
- passing the mask information from the client to AudioFlinger
 and the mixer.
- when using the DIRECT ouput, only verifying the format of
 the track is compatible with the output's for PCM.

Change-Id: I50d87bfb7d7afcabdf5f12d4ab75ef3a54132c0e
diff --git a/include/media/IAudioFlinger.h b/include/media/IAudioFlinger.h
index d8fdc27..4037c46 100644
--- a/include/media/IAudioFlinger.h
+++ b/include/media/IAudioFlinger.h
@@ -48,8 +48,8 @@
                                 pid_t pid,
                                 int streamType,
                                 uint32_t sampleRate,
-                                int format,
-                                int channelCount,
+                                uint32_t format,
+                                uint32_t channelMask,
                                 int frameCount,
                                 uint32_t flags,
                                 const sp<IMemory>& sharedBuffer,
@@ -61,8 +61,8 @@
                                 pid_t pid,
                                 int input,
                                 uint32_t sampleRate,
-                                int format,
-                                int channelCount,
+                                uint32_t format,
+                                uint32_t channelMask,
                                 int frameCount,
                                 uint32_t flags,
                                 int *sessionId,
@@ -73,7 +73,7 @@
      */
     virtual     uint32_t    sampleRate(int output) const = 0;
     virtual     int         channelCount(int output) const = 0;
-    virtual     int         format(int output) const = 0;
+    virtual     uint32_t    format(int output) const = 0;
     virtual     size_t      frameCount(int output) const = 0;
     virtual     uint32_t    latency(int output) const = 0;