[Android][Test] Refactor AccountHolder usage in FirstRunUtilsTest

This CL refactors the AccountHolder usage in FirstRunUtilsTest.

Bug: 1161437
Change-Id: I3baac52615f15ce7457875526220f2cd9cc54748
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2603852Reviewed-by: Wenyu Fu <wenyufu@chromium.org>
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#839557}

chrome/android/javatests/src/org/chromium/chrome/browser/firstrun/FirstRunUtilsTest.java

@@ -4,7 +4,6 @@
 
 package org.chromium.chrome.browser.firstrun;
 
-import android.accounts.Account;
 import android.accounts.AuthenticatorDescription;
 import android.support.test.InstrumentationRegistry;
 
@@ -33,11 +32,6 @@ import org.chromium.content_public.browser.test.util.TestThreadUtils;
 public class FirstRunUtilsTest {
     private FakeAuthenticationAccountManager mAccountManager;
     private AdvancedMockContext mAccountTestingContext;
-    private Account mTestAccount;
-
-    public FirstRunUtilsTest() {
-        mTestAccount = AccountUtils.createAccountFromName("Dummy");
-    }
 
     @Before
     public void setUp() {
@@ -73,7 +67,7 @@ public class FirstRunUtilsTest {
 
     private void addTestAccount() {
         mAccountManager.addAccountHolderBlocking(
-                AccountHolder.builder(mTestAccount).alwaysAccept(true).build());
+                AccountHolder.builder("dummy@gmail.com").alwaysAccept(true).build());
     }
 
     @Test