Add postMessage APIs to the support lib

customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl

Index: customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl
diff --git a/customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl b/customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl
index a4678640cf672dca09d672e0dca17b7bb5912be2..c25c4f77df2e19766de42f4c7af77d1774a88964 100644
--- a/customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl
+++ b/customtabs/src/android/support/customtabs/ICustomTabsCallback.aidl
@@ -22,7 +22,9 @@ import android.os.Bundle;
  * Interface to a CustomTabsCallback.
  * @hide
  */
-oneway interface ICustomTabsCallback {
-    void onNavigationEvent(int navigationEvent, in Bundle extras) = 1;
-    void extraCallback(String callbackName, in Bundle args) = 2;
+interface ICustomTabsCallback {
+    oneway void onNavigationEvent(int navigationEvent, in Bundle extras) = 1;
+    oneway void extraCallback(String callbackName, in Bundle args) = 2;
+    void onMessageChannelReady(in Uri origin, in Bundle extras) = 3;
+    void onPostMessage(String message, in Bundle extras) = 4;
 }