TimeCheck: Dump stack of blocked tids

Test: dedicated "crasher" test, check logcat
Test: adb shell dumpsys media.audio_flinger
Bug: 219958414
Change-Id: I6ec2b2aff2bda2b03c426ce79ffe9ce69c4134d2
diff --git a/media/utils/include/mediautils/TimerThread.h b/media/utils/include/mediautils/TimerThread.h
index ffee602..b69e02c 100644
--- a/media/utils/include/mediautils/TimerThread.h
+++ b/media/utils/include/mediautils/TimerThread.h
@@ -125,6 +125,11 @@
         return s;
     }
 
+    /**
+     * Returns callstack of tid as a string.
+     */
+    static std::string tidCallStackString(pid_t tid);
+
   private:
     // To minimize movement of data, we pass around shared_ptrs to Requests.
     // These are allocated and deallocated outside of the lock.