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

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
index 85540c7dfd12a4cb3bf70173fee29b7ce0d345b6..3fd17f42ef0e882b3c4e1ede7af97f5f589ab360 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SuggestionsSection.java
@@ -9,6 +9,7 @@ import android.support.annotation.Nullable;
 
 import org.chromium.base.Callback;
 import org.chromium.base.Log;
+import org.chromium.base.VisibleForTesting;
 import org.chromium.chrome.browser.ntp.NewTabPageUma;
 import org.chromium.chrome.browser.ntp.snippets.CategoryInt;
 import org.chromium.chrome.browser.ntp.snippets.CategoryStatus;
@@ -101,7 +102,8 @@ public class SuggestionsSection extends InnerNode {
         mStatus.setVisible(!hasSuggestions());
     }
 
-    private static class SuggestionsList extends ChildNode implements Iterable<SnippetArticle> {
+    @VisibleForTesting
+    static class SuggestionsList extends ChildNode implements Iterable<SnippetArticle> {
         private final List<SnippetArticle> mSuggestions = new ArrayList<>();
 
         // TODO(crbug.com/677672): Replace by SuggestionSource when it handles destruction.
@@ -137,7 +139,6 @@ public class SuggestionsSection extends InnerNode {
             ((SnippetArticleViewHolder) holder).onBindViewHolder(suggestion, mCategoryInfo);
         }
 
-        @Override
         public SnippetArticle getSuggestionAt(int position) {
             return mSuggestions.get(position);
         }
@@ -181,6 +182,13 @@ public class SuggestionsSection extends InnerNode {
         }
 
         @Override
+        public void visitItems(NodeVisitor visitor) {
+            for (SnippetArticle suggestion : mSuggestions) {
+                visitor.visitSuggestion(suggestion);
+            }
+        }
+
+        @Override
         public Set<Integer> getItemDismissalGroup(int position) {
             return Collections.singleton(position);
         }
@@ -323,7 +331,7 @@ public class SuggestionsSection extends InnerNode {
         }
     }
 
-    public boolean hasSuggestions() {
+    private boolean hasSuggestions() {
         return mSuggestionsList.getItemCount() != 0;
     }
 
@@ -525,6 +533,10 @@ public class SuggestionsSection extends InnerNode {
         return mHeader;
     }
 
+    SuggestionsList getSuggestionListForTesting() {
+        return mSuggestionsList;
+    }
+
     private class OfflineModelObserver extends SuggestionsOfflineModelObserver<SnippetArticle> {
         public OfflineModelObserver(OfflinePageBridge bridge) {
             super(bridge);