Add option to print peer connection factory Java stack traces.

talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java

Index: talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java
diff --git a/talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java b/talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java
index 6bc8189cd85e80c5fb1987fb297b214ec1a68a0d..0460624aa7c1eb36ab0f41862d8da947d2f83d7a 100644
--- a/talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java
+++ b/talk/app/webrtc/java/src/org/webrtc/PeerConnectionFactory.java
@@ -148,21 +148,23 @@ public class PeerConnectionFactory {
     nativeThreadsCallbacks(nativeFactory);
   }
 
-  public static void printStackTraces() {
-    if (workerThread != null) {
-      Logging.d(TAG, "Worker thread stacks trace:");
-      for (StackTraceElement stackTrace : workerThread.getStackTrace()) {
-        Logging.d(TAG, stackTrace.toString());
-      }
-    }
-    if (signalingThread != null) {
-      Logging.d(TAG, "Signaling thread stacks trace:");
-      for (StackTraceElement stackTrace : signalingThread.getStackTrace()) {
-        Logging.d(TAG, stackTrace.toString());
+  private static void printStackTrace(Thread thread, String threadName) {
+    if (thread != null) {
+      StackTraceElement[] stackTraces = thread.getStackTrace();
+      if (stackTraces.length > 0) {
+        Logging.d(TAG, threadName + " stacks trace:");
+        for (StackTraceElement stackTrace : stackTraces) {
+          Logging.d(TAG, stackTrace.toString());
+        }
       }
     }
   }
 
+  public static void printStackTraces() {
+    printStackTrace(workerThread, "Worker thread");
+    printStackTrace(signalingThread, "Signaling thread");
+  }
+
   private static void onWorkerThreadReady() {
     workerThread = Thread.currentThread();
     Logging.d(TAG, "onWorkerThreadReady");