Add logging to help diagnose a rare bug

Bug: 25911696
Change-Id: Idca44ed873f0a9fa911e9cb1c3a09b4e7e4f23eb
diff --git a/services/audioflinger/Threads.cpp b/services/audioflinger/Threads.cpp
index b9e7a8b..602a0cf 100644
--- a/services/audioflinger/Threads.cpp
+++ b/services/audioflinger/Threads.cpp
@@ -3843,7 +3843,10 @@
                     // because we're about to decrement the last sp<> on those tracks.
                     block = FastMixerStateQueue::BLOCK_UNTIL_ACKED;
                 } else {
-                    LOG_ALWAYS_FATAL("fast track %d should have been active", j);
+                    LOG_ALWAYS_FATAL("fast track %d should have been active; "
+                            "mState=%d, mTrackMask=%#x, recentUnderruns=%u, isShared=%d",
+                            j, track->mState, state->mTrackMask, recentUnderruns,
+                            track->sharedBuffer() != 0);
                 }
                 tracksToRemove->add(track);
                 // Avoids a misleading display in dumpsys