Add postMessage APIs to the support lib

customtabs/src/android/support/customtabs/CustomTabsClient.java

Index: customtabs/src/android/support/customtabs/CustomTabsClient.java
diff --git a/customtabs/src/android/support/customtabs/CustomTabsClient.java b/customtabs/src/android/support/customtabs/CustomTabsClient.java
index f743c7dde92ee3f73648368dc239181506af09e7..8b742a2fd6e8340191c9d3781b601dc09f52a8a0 100644
--- a/customtabs/src/android/support/customtabs/CustomTabsClient.java
+++ b/customtabs/src/android/support/customtabs/CustomTabsClient.java
@@ -175,7 +175,7 @@ public class CustomTabsClient {
      * @param callback The callback through which the client will receive updates about the created
      *                 session. Can be null.
      * @return The session object that was created as a result of the transaction. The client can
-     *         use this to relay {@link CustomTabsSession#mayLaunchUrl(Uri, Bundle, List)} calls.
+     *         use this to relay session specific calls.
      *         Null on error.
      */
     public CustomTabsSession newSession(final CustomTabsCallback callback) {
@@ -186,6 +186,16 @@ public class CustomTabsClient {
             }
 
             @Override
+            public void onMessageChannelReady(Uri origin, Bundle extras) {
+                if (callback != null) callback.onMessageChannelReady(origin, extras);
+            }
+
+            @Override
+            public void onPostMessage(String message, Bundle extras) {
+                if (callback != null) callback.onPostMessage(message, extras);
+            }
+
+            @Override
             public void extraCallback(String callbackName, Bundle args) throws RemoteException {
                 if (callback != null) callback.extraCallback(callbackName, args);
             }