AudioService: Add the AudioDeviceBroker's message queue to the dump

Clogged queue means device-related requests will not be served.

Example dump snippet:

AudioDeviceBroker:
  Message handler (watch for unhandled messages):
    Handler (com.android.server.audio.AudioDeviceBroker$BrokerHandler) {753fed2} @ 359741
      Looper (AudioDeviceBroker, tid 115) {ed3aba3}
        (Total messages: 0, polling=true, quitting=false)

Bug: 135763139
Test: adb shell dumpsys audio
Change-Id: If2130a4bd8bd9536df01656fe1a8f94548912ab9

services/core/java/com/android/server/audio/AudioDeviceBroker.java

@@ -40,9 +40,11 @@ import android.os.PowerManager;
 import android.os.SystemClock;
 import android.os.UserHandle;
 import android.util.Log;
+import android.util.PrintWriterPrinter;
 
 import com.android.internal.annotations.GuardedBy;
 
+import java.io.PrintWriter;
 
 /** @hide */
 /*package*/ final class AudioDeviceBroker {
@@ -597,6 +599,15 @@ import com.android.internal.annotations.GuardedBy;
         }
     }
 
+    /*package*/ void dump(PrintWriter pw, String prefix) {
+        if (mBrokerHandler != null) {
+            pw.println(prefix + "Message handler (watch for unhandled messages):");
+            mBrokerHandler.dump(new PrintWriterPrinter(pw), prefix + "  ");
+        } else {
+            pw.println("Message handler is null");
+        }
+    }
+
     //---------------------------------------------------------------------
     // Internal handling of messages
     // These methods are ALL synchronous, in response to message handling in BrokerHandler

services/core/java/com/android/server/audio/AudioService.java

@@ -6421,11 +6421,12 @@ public class AudioService extends IAudioService.Stub
 
         dumpAudioPolicies(pw);
         mDynPolicyLogger.dump(pw);
-
         mPlaybackMonitor.dump(pw);
-
         mRecordMonitor.dump(pw);
 
+        pw.println("\nAudioDeviceBroker:");
+        mDeviceBroker.dump(pw, "  ");
+
         pw.println("\n");
         pw.println("\nEvent logs:");
         mModeLogger.dump(pw);