Add postMessage APIs to the support lib

customtabs/src/android/support/customtabs/ICustomTabsService.aidl

Index: customtabs/src/android/support/customtabs/ICustomTabsService.aidl
diff --git a/customtabs/src/android/support/customtabs/ICustomTabsService.aidl b/customtabs/src/android/support/customtabs/ICustomTabsService.aidl
index e53ca84e234a5926febd4defd9859a45366f06ab..b0c601060bdf4a32b4d51ca62d9995c975f12578 100644
--- a/customtabs/src/android/support/customtabs/ICustomTabsService.aidl
+++ b/customtabs/src/android/support/customtabs/ICustomTabsService.aidl
@@ -33,4 +33,6 @@ interface ICustomTabsService {
             in Bundle extras, in List<Bundle> otherLikelyBundles) = 3;
     Bundle extraCommand(String commandName, in Bundle args) = 4;
     boolean updateVisuals(in ICustomTabsCallback callback, in Bundle bundle) = 5;
+    boolean validatePostMessageOrigin(in ICustomTabsCallback callback) = 6;
+    int postMessage(in ICustomTabsCallback callback, String message, in Bundle extras) = 7;
 }