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

Bug: 10349083
Change-Id: I4a94b1eac53df57c05103913bd593d92b1e062d7
diff --git a/core/java/android/os/Looper.java b/core/java/android/os/Looper.java
index 9b3880b..34c880f 100644
--- a/core/java/android/os/Looper.java
+++ b/core/java/android/os/Looper.java
@@ -273,6 +273,7 @@
         mQueue.dump(pw, prefix + "  ");
     }
 
+    @Override
     public String toString() {
         return "Looper (" + mThread.getName() + ", tid " + mThread.getId()
                 + ") {" + Integer.toHexString(System.identityHashCode(this)) + "}";