[Reland] Refactor WebappRegistry into a singleton instance.

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

Index: chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestBase.java
diff --git a/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestBase.java b/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestBase.java
index ec1f26a1bd1fb623e199c01278aef335753d9c5c..e63b80f5f4cd68e990db62e09173a9e072aad64e 100644
--- a/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestBase.java
+++ b/chrome/android/javatests/src/org/chromium/chrome/browser/webapps/WebappActivityTestBase.java
@@ -92,16 +92,12 @@ public abstract class WebappActivityTestBase extends ChromeActivityTestCaseBase<
     protected void setUp() throws Exception {
         super.setUp();
 
-        // Register the webapp 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(
-                WEBAPP_ID, new WebappRegistry.FetchWebappDataStorageCallback() {
-                    @Override
-                    public void onWebappDataStorageRetrieved(WebappDataStorage storage) {
-                        storage.updateFromShortcutIntent(createIntent());
-                    }
-                });
+        // Register the webapp so when the data storage is opened, the test doesn't crash.
+        WebappRegistry.refreshSharedPrefsForTesting();
+        TestFetchStorageCallback callback = new TestFetchStorageCallback();
+        WebappRegistry.getInstance().register(WEBAPP_ID, callback);
+        callback.waitForCallback(0);
+        callback.getStorage().updateFromShortcutIntent(createIntent());
     }
 
     /**