protected Uri getLaunchingUrl() {
        Uri uri = getIntent().getData();
        if (uri != null) {
            Log.d(TAG, "Using URL from Intent (" + uri + ").");
            return uri;
        }

        if (mMetadata.defaultUrl != null) {
            Log.d(TAG, "Using URL from Manifest (" + mMetadata.defaultUrl + ").");
            return Uri.parse(mMetadata.defaultUrl);
        }

        return Uri.parse("https://www.example.com/");
    }
Returns the URL that the Trusted Web Activity should be launched to. By default this
implementation checks to see if the Activity was launched with an Intent with data, if so
attempt to launch to that URL. If not, read the
"android.support.customtabs.trusted.DEFAULT_URL" metadata from the manifest.

Override this for special handling (such as ignoring or sanitising data from the Intent).
customtabs/src/android/support/customtabs/trusted/LauncherActivity.java