[Reland] Refactor WebappRegistry into a singleton instance.

chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappModeTest.java

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.webapps;
 
 import android.app.Activity;
 import android.content.Context;
 import android.content.Intent;
 import android.content.SharedPreferences;
@@ skipping 75 matching lines @@
         Intent intent = createIntent(id, url, title, icon, addMac);
 
         getInstrumentation().getTargetContext().startActivity(intent);
         getInstrumentation().waitForIdleSync();
         ApplicationTestUtils.waitUntilChromeInForeground();
     }
 
     @Override
     public void setUp() throws Exception {
         super.setUp();
+        WebappRegistry.refreshSharedPrefsForTesting();
 
         // Register the webapps so when the data storage is opened, the test doesn't crash. There is
         // no race condition with the retrieval as AsyncTasks are run sequentially on the background
         // thread.
-        WebappRegistry.registerWebapp(
+        WebappRegistry.getInstance().register(
                 WEBAPP_1_ID, new WebappRegistry.FetchWebappDataStorageCallback() {
                     @Override
                     public void onWebappDataStorageRetrieved(WebappDataStorage storage) {
                         storage.updateFromShortcutIntent(createIntent(
                                 WEBAPP_1_ID, WEBAPP_1_URL, WEBAPP_1_TITLE, WEBAPP_ICON, true));
                     }
                 });
-        WebappRegistry.registerWebapp(
+        WebappRegistry.getInstance().register(
                 WEBAPP_2_ID, new WebappRegistry.FetchWebappDataStorageCallback() {
                     @Override
                     public void onWebappDataStorageRetrieved(WebappDataStorage storage) {
                         storage.updateFromShortcutIntent(createIntent(
                                 WEBAPP_1_ID, WEBAPP_1_URL, WEBAPP_1_TITLE, WEBAPP_ICON, true));
                     }
                 });
     }
 
     /**
@@ skipping 204 matching lines @@
 
         WebappActivity webappActivity = (WebappActivity) lastActivity;
         if (webappActivity.getActivityTab() == null) return false;
 
         View rootView = webappActivity.findViewById(android.R.id.content);
         if (!rootView.hasWindowFocus()) return false;
 
         return true;
     }
 }