[Reland] Refactor WebappRegistry into a singleton instance.

chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java

Index: chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java b/chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java
index f1609df31ec8653afeb50f57a6384c72d498c323..8dc2a08d323d2e817ec04ef56b377a40b7566d23 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/DeferredStartupHandler.java
@@ -48,6 +48,7 @@ import org.chromium.chrome.browser.preferences.privacy.PrivacyPreferencesManager
 import org.chromium.chrome.browser.share.ShareHelper;
 import org.chromium.chrome.browser.webapps.ChromeWebApkHost;
 import org.chromium.chrome.browser.webapps.WebApkVersionManager;
+import org.chromium.chrome.browser.webapps.WebappRegistry;
 import org.chromium.content.browser.ChildProcessLauncher;
 
 import java.util.ArrayList;
@@ -173,6 +174,10 @@ public class DeferredStartupHandler {
         mDeferredTasks.add(new Runnable() {
             @Override
             public void run() {
+                // Initialize the WebappRegistry if it's not already initialized. Must be done on
+                // the main thread.
+                WebappRegistry.getInstance();
+
                 // Punt all tasks that may block on disk off onto a background thread.
                 initAsyncDiskTask();
 
@@ -276,11 +281,21 @@ public class DeferredStartupHandler {
                             SystemClock.uptimeMillis() - asyncTaskStartTime,
                             TimeUnit.MILLISECONDS);
 
+                    // Warm up all web app shared prefs. This must be run after the WebappRegistry
+                    // instance is initialized.
+                    WebappRegistry.warmUpSharedPrefs();
+
                     return null;
                 } finally {
                     TraceEvent.end("ChromeBrowserInitializer.onDeferredStartup.doInBackground");
                 }
             }
+
+            @Override
+            protected void onPostExecute(Void params) {
+                // Must be run on the UI thread after the WebappRegistry has been completely warmed.
+                WebappRegistry.getInstance().unregisterOldWebapps(System.currentTimeMillis());
+            }
         }.executeOnExecutor(AsyncTask.THREAD_POOL_EXECUTOR);
     }