AudioMixer new cmd: remove sample rate converter

Add a new command REMOVE to remove any sample rate converter
   on a track, without having to delete the track name.
Add comments.
Remove some dead code.
Fix whitespace and comparison to NULL.

Change-Id: Id55a23ab5ee673189e99675b4e6fa5df7b617987
diff --git a/services/audioflinger/AudioMixer.cpp b/services/audioflinger/AudioMixer.cpp
index 05fa3b9..100f289 100644
--- a/services/audioflinger/AudioMixer.cpp
+++ b/services/audioflinger/AudioMixer.cpp
@@ -327,15 +327,9 @@
         track.enabled = false;
         invalidateState(1<<name);
     }
-    if (track.resampler != NULL) {
-        // delete the resampler
-        delete track.resampler;
-        track.resampler = NULL;
-        track.sampleRate = mSampleRate;
-        invalidateState(1<<name);
-    }
-    track.volumeInc[0] = 0;
-    track.volumeInc[1] = 0;
+    // delete the resampler
+    delete track.resampler;
+    track.resampler = NULL;
     mTrackNames &= ~(1<<name);
 }
 
@@ -439,6 +433,12 @@
             track.resetResampler();
             invalidateState(1 << name);
             break;
+        case REMOVE:
+            delete track.resampler;
+            track.resampler = NULL;
+            track.sampleRate = mSampleRate;
+            invalidateState(1 << name);
+            break;
         default:
             LOG_FATAL("bad param");
         }
@@ -499,7 +499,7 @@
 
 bool AudioMixer::track_t::setResampler(uint32_t value, uint32_t devSampleRate)
 {
-    if (value!=devSampleRate || resampler) {
+    if (value != devSampleRate || resampler != NULL) {
         if (sampleRate != value) {
             sampleRate = value;
             if (resampler == NULL) {