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

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/OptionalLeaf.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/OptionalLeaf.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/OptionalLeaf.java
index 7bda849695ebe655abc73973361dec34264e00d6..be350eecf430d3547bd4c6f4483304f97f33d8d6 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/OptionalLeaf.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/OptionalLeaf.java
@@ -58,6 +58,11 @@ public abstract class OptionalLeaf extends ChildNode {
         dismiss(itemRemovedCallback);
     }
 
+    @Override
+    public final void visitItems(NodeVisitor visitor) {
+        if (mVisible) visitOptionalItem(visitor);
+    }
+
     /** @return Whether the optional item is currently visible. */
     public final boolean isVisible() {
         return mVisible;
@@ -112,4 +117,10 @@ public abstract class OptionalLeaf extends ChildNode {
     protected void dismiss(Callback<String> itemRemovedCallback) {
         assert false;
     }
+
+    /**
+     * Visits this item. This method is called iff the optional item is currently visible.
+     * @param visitor The visitor with which to visit this item.
+     */
+    protected abstract void visitOptionalItem(NodeVisitor visitor);
 }