[Android][WebSignin] Remove AccountPickerDelegate#goIncognitoMode()

This CL removes the method AccountPickerDelegate#goIncognitoMode() as
the incognito related actions will be handled in a separate MVC package.

Bug: 1120350
Change-Id: I09ad7b3465974ff4c7c41bedd155bf71d1164de6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2391067Reviewed-by: Rohit Agarwal <roagarwal@chromium.org>
Commit-Queue: Alice Wang <aliceywang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804197}

chrome/android/java/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerBottomSheetMediator.java

@@ -87,7 +87,6 @@ class AccountPickerBottomSheetMediator implements AccountPickerCoordinator.Liste
     @Override
     public void goIncognitoMode() {
         mModel.set(AccountPickerBottomSheetProperties.VIEW_STATE, ViewState.INCOGNITO_INTERSTITIAL);
-        mAccountPickerDelegate.goIncognitoMode();
     }
 
     /**

chrome/android/java/src/org/chromium/chrome/browser/signin/account_picker/AccountPickerDelegate.java

@@ -112,11 +112,6 @@ public class AccountPickerDelegate implements WebSigninBridge.Listener {
                 });
     }
 
-    /**
-     * Notifies when the user clicked the "Go incognito mode" button.
-     */
-    public void goIncognitoMode() {}
-
     /**
      * Sign-in completed successfully and the primary account is available in the cookie jar.
      */

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

@@ -382,7 +382,6 @@ public class AccountPickerBottomSheetTest {
         buildAndShowExpandedBottomSheet();
         onView(withText(R.string.signin_incognito_mode_secondary)).check(matches(isDisplayed()));
         onView(withText(R.string.signin_incognito_mode_primary)).perform(click());
-        verify(mAccountPickerDelegateMock).goIncognitoMode();
         checkIncognitoInterstitialSheet();
     }