[Signin][Android] Wipe account list in OAuth2TokenService test

This CL addsSigninTestUtil.resetSigninState call to
OAuth2TokenServiceIntegrationTest.tearDown, so all signin-related prefs
are wiped and the state doesn't leak from the test.

Bug: 908542
Change-Id: I43b37d76bd24e14687a4e9d0ab35d2e88d283f6f
Reviewed-on: https://chromium-review.googlesource.com/c/1369940Reviewed-by: Mihai Sardarescu <msarda@chromium.org>
Commit-Queue: Boris Sazonov <bsazonov@chromium.org>
Cr-Commit-Position: refs/heads/master@{#615472}

chrome/android/javatests/src/org/chromium/chrome/browser/signin/OAuth2TokenServiceIntegrationTest.java

@@ -20,6 +20,7 @@ import org.chromium.base.test.BaseJUnit4ClassRunner;
 import org.chromium.base.test.util.RetryOnFailure;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.chrome.test.util.ApplicationData;
+import org.chromium.chrome.test.util.browser.signin.SigninTestUtil;
 import org.chromium.components.signin.AccountIdProvider;
 import org.chromium.components.signin.AccountManagerFacade;
 import org.chromium.components.signin.ChromeSigninController;
@@ -88,6 +89,7 @@ public class OAuth2TokenServiceIntegrationTest {
             mOAuth2TokenService.validateAccounts(false);
         });
         SigninHelper.resetSharedPrefs();
+        SigninTestUtil.resetSigninState();
     }
 
     private void mapAccountNamesToIds() {