Revert "Reapply "AudioFlinger: Control volume using Port ID""

This reverts commit af273c6817b7e6b004034aad4f451eb87273dd62.

Reason for revert: DroidMonitor. Potential culprit for http://b/361843371 - verifying through ABTD session before submission. 

Change-Id: I21918f26c06793cab65b7052c429aa7249dc489f
diff --git a/services/audioflinger/TrackBase.h b/services/audioflinger/TrackBase.h
index 1342b7b..a0b85f7 100644
--- a/services/audioflinger/TrackBase.h
+++ b/services/audioflinger/TrackBase.h
@@ -347,7 +347,7 @@
     size_t              mBufferSize; // size of mBuffer in bytes
     // we don't really need a lock for these
     MirroredVariable<track_state>  mState;
-    audio_attributes_t  mAttr;
+    const audio_attributes_t mAttr;
     const uint32_t      mSampleRate;    // initial sample rate only; for tracks which
                         // support dynamic rates, the current value is in control block
     const audio_format_t mFormat;