@Override
        public void onCustomTabsServiceConnected(ComponentName componentName,
                CustomTabsClient client) {
            if (TrustedWebUtils.warmupIsRequired(mContext, mProviderPackage)) {
                client.warmup(0);
            }
            mSession = client.newSession(null, mSessionId);

            if (mSession != null && mOnSessionCreatedRunnable != null) {
                mOnSessionCreatedRunnable.run();
            } else if (mSession == null && mOnSessionCreationFailedRunnable != null) {
                mOnSessionCreationFailedRunnable.run();
            }

            mOnSessionCreatedRunnable = null;
            mOnSessionCreationFailedRunnable = null;
        }
Returns package name of the browser this TwaLauncher is launching.
customtabs/src/android/support/customtabs/trusted/TwaLauncher.java