media.log cleanup

Remove almost all of the specific logs, but leave the media.log
logging infrastructure in place for the next time we need it.

Re-apply a few good changes that were reverted earlier:
 - check logf format vs. argument list compatibility
 - distinguish potentially modified and actually modified tracks in FastMixer
 - fix benign bug where sq->end() was called more than once
 - fix a build warning

Bug: 6490974
Change-Id: I02d3e83646c738acaebb415bd0d6b548638b4ef5
diff --git a/services/audioflinger/AudioMixer.cpp b/services/audioflinger/AudioMixer.cpp
index 17b6a8a..7d38f80 100644
--- a/services/audioflinger/AudioMixer.cpp
+++ b/services/audioflinger/AudioMixer.cpp
@@ -122,6 +122,7 @@
     mState.hook         = process__nop;
     mState.outputTemp   = NULL;
     mState.resampleTemp = NULL;
+    mState.mLog         = &mDummyLog;
     // mState.reserved
 
     // FIXME Most of the following initialization is probably redundant since
@@ -169,6 +170,11 @@
     delete [] mState.resampleTemp;
 }
 
+void AudioMixer::setLog(NBLog::Writer *log)
+{
+    mState.mLog = log;
+}
+
 int AudioMixer::getTrackName(audio_channel_mask_t channelMask, int sessionId)
 {
     uint32_t names = (~mTrackNames) & mConfiguredNames;
@@ -620,7 +626,6 @@
 }
 
 
-
 void AudioMixer::process(int64_t pts)
 {
     mState.hook(&mState, pts);