Add support for non-blocking I/O with Looper.

Bug: 10349083
Change-Id: I4a94b1eac53df57c05103913bd593d92b1e062d7
diff --git a/core/jni/android_os_MessageQueue.h b/core/jni/android_os_MessageQueue.h
index 49d2aa0..1e49b5f 100644
--- a/core/jni/android_os_MessageQueue.h
+++ b/core/jni/android_os_MessageQueue.h
@@ -22,7 +22,7 @@
 
 namespace android {
 
-class MessageQueue : public RefBase {
+class MessageQueue : public virtual RefBase {
 public:
     /* Gets the message queue's looper. */
     inline sp<Looper> getLooper() const {