public CustomTabsSession getSession() {
        if (mClient == null) {
            mCustomTabsSession = null;
        } else if (mCustomTabsSession == null) {
            mCustomTabsSession = mClient.newSession(null);
        }
        return mCustomTabsSession;
    }
Creates or retrieves an exiting CustomTabsSession.

@return a CustomTabsSession.
demos/src/main/java/org/chromium/customtabsdemos/CustomTabActivityHelper.java