[Suggestions] Remove TreeNode.getSuggestionAt() in favor of a visitor.

chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SignInPromo.java

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chrome.browser.ntp.cards;
 
 import android.content.Context;
 import android.support.annotation.DrawableRes;
 import android.support.annotation.Nullable;
 import android.support.annotation.StringRes;
@@ skipping 42 matching lines @@
         } else {
             mObserver = new SigninObserver(signinManager);
             uiDelegate.addDestructionObserver(mObserver);
         }
 
         setVisible(signinManager.isSignInAllowed() && !signinManager.isSignedInOnNative());
     }
 
     @Override
     @ItemViewType
-    public int getItemViewType() {
+    protected int getItemViewType() {
         return ItemViewType.PROMO;
     }
 
     /**
      * @return a {@link DestructionObserver} observer that updates the visibility of the signin
      * promo and unregisters itself when the New Tab Page is destroyed.
      */
     @Nullable
     public DestructionObserver getObserver() {
         return mObserver;
     }
 
     @Override
-    public void onBindViewHolder(NewTabPageViewHolder holder) {
+    protected void onBindViewHolder(NewTabPageViewHolder holder) {
         assert holder instanceof StatusCardViewHolder;
         ((StatusCardViewHolder) holder).onBindViewHolder(this);
         mImpressionTracker.reset(mImpressionTracker.wasTriggered() ? null : holder.itemView);
     }
 
     @Override
+    protected void visitOptionalItem(NodeVisitor visitor) {
+        visitor.visitSignInPromo();
+    }
+
+    @Override
     @StringRes
     public int getHeader() {
         return R.string.snippets_disabled_generic_prompt;
     }
 
     @Override
     public String getDescription() {
         return ContextUtils.getApplicationContext().getString(
                 R.string.snippets_disabled_signed_out_instructions);
     }
@@ skipping 93 matching lines @@
                     R.dimen.ntp_sign_in_promo_margin_top);
         }
 
         @DrawableRes
         @Override
         protected int selectBackground(boolean hasCardAbove, boolean hasCardBelow) {
             return R.drawable.ntp_signin_promo_card_single;
         }
     }
 }