[Android][Test] Refactor SyncTestRule#signinAndEnableSync()

This CL refactors SyncTestRule#signinAndEnableSync() to
use SigninTestUtil to handle sign-in.

Bug: 1126814
Change-Id: I171e9c59e8616236ede6d2aa247ec826577b7d67
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2401144Reviewed-by: Marc Treib <treib@chromium.org>
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#806922}

chrome/android/javatests/src/org/chromium/chrome/browser/sync/SyncTest.java

@@ -56,7 +56,7 @@ public class SyncTest {
 
         // Signing back in should re-enable sync.
         mSyncTestRule.signinAndEnableSync(account);
-        SyncTestUtil.waitForSyncActive();
+        Assert.assertTrue("Sync should be re-enabled.", SyncTestUtil.isSyncActive());
     }
 
     @Test

chrome/android/javatests/src/org/chromium/chrome/browser/sync/SyncTestRule.java

@@ -33,6 +33,7 @@ import org.chromium.chrome.browser.signin.SigninManager;
 import org.chromium.chrome.browser.signin.UnifiedConsentServiceBridge;
 import org.chromium.chrome.test.ChromeActivityTestRule;
 import org.chromium.chrome.test.util.browser.signin.AccountManagerTestRule;
+import org.chromium.chrome.test.util.browser.signin.SigninTestUtil;
 import org.chromium.chrome.test.util.browser.sync.SyncTestUtil;
 import org.chromium.components.signin.base.CoreAccountInfo;
 import org.chromium.components.signin.metrics.SigninAccessPoint;
@@ -236,7 +237,10 @@ public class SyncTestRule extends ChromeActivityTestRule<ChromeActivity> {
     }
 
     public void signinAndEnableSync(final Account account) {
-        signinAndEnableSyncInternal(account, true);
+        SigninTestUtil.signIn(account, mProfileSyncService);
+        enableUKM();
+        SyncTestUtil.waitForSyncActive();
+        SyncTestUtil.triggerSyncAndWaitForCompletion();
     }
 
     public void signOut() {

chrome/test/android/javatests/src/org/chromium/chrome/test/util/browser/signin/SigninTestUtil.java

@@ -29,7 +29,7 @@ import java.util.concurrent.TimeoutException;
 /**
  * Utility class for test signin functionality.
  */
-final class SigninTestUtil {
+public final class SigninTestUtil {
     /**
      * Returns the currently signed in account.
      */
@@ -43,9 +43,11 @@ final class SigninTestUtil {
     }
 
     /**
-     * Sign into an account.
+     * Signs into an account and enables the sync if given a {@link ProfileSyncService} object.
+     *
+     * @param profileSyncService Enable the sync with it if it is not null.
      */
-    static void signIn(Account account, @Nullable ProfileSyncService profileSyncService) {
+    public static void signIn(Account account, @Nullable ProfileSyncService profileSyncService) {
         CallbackHelper callbackHelper = new CallbackHelper();
         TestThreadUtils.runOnUiThreadBlocking(() -> {
             SigninManager signinManager = IdentityServicesProvider.get().getSigninManager(