Adding a router class to handle messages that expect responses.

mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java

Index: mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
diff --git a/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java b/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
index 0288678a022d342a8d085cfc14f6e25430a029c4..d94796831b0e28de4c8995435671adbba586b5a1 100644
--- a/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
+++ b/mojo/bindings/java/src/org/chromium/mojo/bindings/BindingsHelper.java
@@ -4,6 +4,9 @@
 
 package org.chromium.mojo.bindings;
 
+import org.chromium.mojo.system.AsyncWaiter;
+import org.chromium.mojo.system.Handle;
+
 /**
  * Helper functions.
  */
@@ -73,4 +76,17 @@ public class BindingsHelper {
     private static boolean isSurrogate(char c) {
         return c >= Character.MIN_SURROGATE && c < (Character.MAX_SURROGATE + 1);
     }
+
+    /**
+     * Returns an {@link AsyncWaiter} to use with the given handle, or <code>null</code> if none if
+     * available.
+     */
+    static AsyncWaiter getDefaultAsyncWaiterForHandle(Handle handle) {
+        if (handle.getCore() != null) {
+            return handle.getCore().getDefaultAsyncWaiter();
+        } else {
+            return null;
+        }
+    }
+
 }