Ntp: use callbacks for partial binding, they can carry more detail.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java
index 75248d2985e267326054f9450029fadc051da9b3..add59f29ff51024cf3c9429e75f47fe0e9f26715 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageViewHolder.java
@@ -7,12 +7,21 @@ package org.chromium.chrome.browser.ntp.cards;
 import android.support.v7.widget.RecyclerView;
 import android.view.View;
 
+import org.chromium.base.Callback;
+
 /**
  * Holds metadata about an item we want to display on the NTP. An item can be anything that will be
  * displayed on the NTP {@link RecyclerView}.
  */
 public class NewTabPageViewHolder extends RecyclerView.ViewHolder {
     /**
+     * A single instance of {@link UpdateLayoutParamsCallback} that can be reused as it has no
+     * state.
+     */
+    public static final UpdateLayoutParamsCallback UPDATE_LAYOUT_PARAMS_CALLBACK =
+            new UpdateLayoutParamsCallback();
+
+    /**
      * Constructs a {@link NewTabPageViewHolder} used to display an part of the NTP (e.g., header,
      * article snippet, above-the-fold view, etc.)
      *
@@ -39,4 +48,24 @@ public class NewTabPageViewHolder extends RecyclerView.ViewHolder {
     protected RecyclerView.LayoutParams getParams() {
         return (RecyclerView.LayoutParams) itemView.getLayoutParams();
     }
+
+    /**
+     * A callback to perform a partial bind on a {@link NewTabPageViewHolder}.
+     * @see org.chromium.chrome.browser.ntp.cards.InnerNode#notifyItemChanged(int,
+     * PartialBindCallback)
+     *
+     * This empty class is used to strengthen type assertions, as those would be less useful with a
+     * generic class due to type erasure.
+     */
+    public abstract static class PartialBindCallback extends Callback<NewTabPageViewHolder> {}
+
+    /**
+     * Callback to update the layout params for the view holder.
+     */
+    public static class UpdateLayoutParamsCallback extends PartialBindCallback {
+        @Override
+        public void onResult(NewTabPageViewHolder holder) {
+            holder.updateLayoutParams();
+        }
+    }
 }