FastMixer update

Updates:
 - Add support for mono fast tracks
 - Add support for optional sample rate conversion on fast tracks
 - Log sample rate and frame count
 - Enable statistics

Change-Id: Ife014edf4f452da361f3eaaae19209ef6ff6958b
diff --git a/services/audioflinger/FastMixer.h b/services/audioflinger/FastMixer.h
index b24f2eb..8a8fcb8 100644
--- a/services/audioflinger/FastMixer.h
+++ b/services/audioflinger/FastMixer.h
@@ -58,6 +58,8 @@
     uint32_t mWriteErrors;      // total number of write() errors
     uint32_t mUnderruns;        // total number of underruns
     uint32_t mOverruns;         // total number of overruns
+    uint32_t mSampleRate;
+    size_t   mFrameCount;
 #ifdef FAST_MIXER_STATISTICS
     // cycle times in seconds
     float    mMean;