PortionsOfCustomTabsConnection.java

        ThreadUtils.postOnUiThread(new Runnable() {
            @Override
            public void run() {
                try {
                    TraceEvent.begin("CustomTabsConnection.warmupInternal");
                    // Warmup is done in several steps, some of them can happen only once.

                    // Step 1: Only once: Initialize the browser.
                    if (!initialized) initializeBrowser(mApplication);

                    // Step 2: Can happen more than once: Create a spare renderer. It takes time,
                    // other threads and processes, so start it sooner rather than later.
                    if (mayCreateSpareWebContents && mSpeculation == null
                            && !SysUtils.isLowEndDevice()) {
                        WarmupManager.getInstance().createSpareWebContents();
                    }

                    if (!initialized) {
                        // Step 3: Only once: Create the ResourcePrefetchPredictor. It triggers work
                        // on other threads, start early.
                        Profile profile = Profile.getLastUsedProfile();
                        new ResourcePrefetchPredictor(profile).startInitialization();

                        // Step 4: Only once: Access the shared preferences for the first time. The
                        // throttling database uses shared preferences, that can cause a StrictMode
                        // violation on the first access. Make sure that this access is not in
                        // mayLauchUrl.
                        RequestThrottler.getForUid(mApplication, uid);
                    }
                } finally {
                    TraceEvent.end("CustomTabsConnection.warmupInternal");
                }
                mWarmupHasBeenFinished.set(true);
            }
        });