@Override
    public void onDisconnectChannel(Context appContext) {
        unbindFromContext(appContext);
    }
Posts a message to the client. This should be called when a tab controlled by related
{@link CustomTabsSession} has sent a postMessage. If postMessage() is called from a single
thread, then the messages will be posted in the same order.

@param message The message sent.
@param extras Reserved for future use.
@return Whether the postMessage was sent to the remote successfully.
customtabs/src/android/support/customtabs/PostMessageServiceConnection.java