[Android][Test] Test AccountPickerDelegate#isIncognitoModeEnabled

This CL adds a test for the method
AccountPickerDelegate#isIncognitoModeEnabled().

Bug: 1149866
Change-Id: I81518ee322d7942ff2482e85683c04a2acf216e0
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2544943Reviewed-by: Tanmoy Mollik <triploblastic@chromium.org>
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#828664}

chrome/android/junit/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerDelegateTest.java

@@ -32,6 +32,7 @@ import org.robolectric.Robolectric;
 
 import org.chromium.base.Callback;
 import org.chromium.base.test.BaseRobolectricTestRunner;
+import org.chromium.chrome.browser.incognito.IncognitoUtils;
 import org.chromium.chrome.browser.profiles.Profile;
 import org.chromium.chrome.browser.signin.IdentityServicesProvider;
 import org.chromium.chrome.browser.signin.SigninManager;
@@ -116,6 +117,7 @@ public class AccountPickerDelegateTest {
 
     @After
     public void tearDown() {
+        IncognitoUtils.setEnabledForTesting(null);
         mDelegate.onDismiss();
     }
 
@@ -184,4 +186,12 @@ public class AccountPickerDelegateTest {
                                            AccountManagerTestRule.TEST_ACCOUNT_EMAIL),
                         mActivity, callback);
     }
+
+    @Test
+    public void testIsIncognitoModeEnabled() {
+        IncognitoUtils.setEnabledForTesting(true);
+        Assert.assertTrue(mDelegate.isIncognitoModeEnabled());
+        IncognitoUtils.setEnabledForTesting(false);
+        Assert.assertFalse(mDelegate.isIncognitoModeEnabled());
+    }
 }