Add new NTP layout with snippet cards and hide it behind a flag

chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/NewTabPageAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/NewTabPageAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/NewTabPageAdapter.java
new file mode 100644
index 0000000000000000000000000000000000000000..31bfb3b8b1ecab23ddf7064bdc5e800d905efd8b
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/NewTabPageAdapter.java
@@ -0,0 +1,105 @@
+// 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.snippets;
+
+import android.support.v7.widget.RecyclerView.Adapter;
+import android.view.ViewGroup;
+
+import org.chromium.chrome.browser.ntp.NewTabPageCardsManager;
+import org.chromium.chrome.browser.ntp.NewTabPageCardsManager.AboveTheFoldListItem;
+import org.chromium.chrome.browser.ntp.NewTabPageCardsManager.NewTabPageListItem;
+import org.chromium.chrome.browser.ntp.NewTabPageLayout;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+* A class that represents the adapter backing the NTP RecyclerView. The first element should always

[newt (away), 2016/03/23 05:29:38]

Simpler: "The adapter backing the NTP RecyclerView."

"represents" is an overused word in class documentation. Most classes simply
*are* something, rather than *representing* something.

[May, 2016/03/23 19:22:57]

Acknowledged. Merged this into NewTabPageCardsManager.

+* be the NTP above contents view, and subsequent elements are the cards to show to the user.

[newt (away), 2016/03/23 05:29:39]

What is "NTP above contents view"? Maybe: "the above-the-fold NTP contents
(logo, search box, most visited tiles)"

[May, 2016/03/23 19:22:57]

Acknowledged. Merged this into NewTabPageCardsManager.

+*/
+public class NewTabPageAdapter extends Adapter<NewTabPageListItemViewHolder> {
+    class NewTabPageAboveTheFoldViewHolder extends NewTabPageListItemViewHolder {

[newt (away), 2016/03/23 05:29:38]

static

[May, 2016/03/23 19:22:57]

Done.

+        public NewTabPageAboveTheFoldViewHolder(NewTabPageLayout view, SnippetsManager manager) {
+            super(view, manager);
+        }
+
+        @Override
+        public void onBindViewHolder(NewTabPageListItem snippetItem) {
+            // nothing to do
+        }
+    }
+
+    private List<NewTabPageListItem> mNewTabPageListItems;

[newt (away), 2016/03/23 05:29:39]

might as well make these all final

[May, 2016/03/23 19:22:57]

Done.

+    private final SnippetsManager mManager;
+    private AboveTheFoldListItem mNewTabPageAboveTheFoldItem;
+    private NewTabPageLayout mAboveTheFoldView;
+
+    /**
+     * Constructs a SnippetsAdapter object that backs the Snippets RecyclerView on the NTP
+     *
+     * @param snippetsManager SnippetsManager object used to open an article
+     */
+    public NewTabPageAdapter(SnippetsManager snippetsManager, NewTabPageLayout aboveTheFoldLayout) {
+        mManager = snippetsManager;
+        mNewTabPageListItems = new ArrayList<NewTabPageListItem>();
+        mAboveTheFoldView = aboveTheFoldLayout;

[newt (away), 2016/03/23 05:29:38]

Be consistent in your variable names. Unless there's a good reason to deviate,
the parameter name should match the member variable name. Variable names across
classes should be consistent too. I should be able to find all the places this
variable gets passed around between classes by grepping for "mAboveTheFoldView"
(or whatever you decide to call it).

You could even call this mNewTabPageLayout; then you don't need to create new
"aboveTheFold" terminology.

[May, 2016/03/23 19:22:57]

Done.

+    }
+
+    public void setAboveTheFoldItem(AboveTheFoldListItem item) {

[newt (away), 2016/03/23 05:29:38]

Why is this method even needed? We can simply do "mNewTabPageListItems.add(new
AboveTheFoldListItem())" in the constructor of this class.

[May, 2016/03/23 19:22:57]

Done.

+        mNewTabPageAboveTheFoldItem = item;
+        if (mNewTabPageListItems.size() == 0) {
+            mNewTabPageListItems.add(item);
+        } else {
+            mNewTabPageListItems.set(0, mNewTabPageAboveTheFoldItem);
+        }
+        notifyDataSetChanged();
+    }
+
+    /**
+     * Set the list of items to display in the snippets RecyclerView

[newt (away), 2016/03/23 05:29:39]

nit: s/Set/Sets/

[May, 2016/03/23 19:22:57]

Done.

+     *
+     * @param listItems the new list of items to display
+     */
+    public void setSnippetListItems(List<NewTabPageListItem> listItems) {
+        mNewTabPageListItems.clear();
+        mNewTabPageListItems.add(mNewTabPageAboveTheFoldItem);
+        mNewTabPageListItems.addAll(listItems);
+        notifyDataSetChanged();
+    }
+
+    @Override
+    public int getItemViewType(int position) {
+        return mNewTabPageListItems.get(position).getType();
+    }
+
+    @Override
+    public NewTabPageListItemViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        if (viewType == NewTabPageCardsManager.SNIPPET_ITEM_ABOVE_THE_FOLD) {
+            return new NewTabPageAboveTheFoldViewHolder(mAboveTheFoldView, mManager);
+        }
+
+        if (viewType == NewTabPageCardsManager.SNIPPET_ITEM_TYPE_HEADER) {
+            return new SnippetHeaderItemViewHolder(
+                    SnippetHeaderItemViewHolder.createView(parent), mManager);
+        }
+
+        if (viewType == NewTabPageCardsManager.SNIPPET_ITEM_TYPE_SNIPPET) {
+            return new SnippetCardItemViewHolder(
+                    SnippetCardItemViewHolder.createView(parent), mManager);
+        }
+
+        return null;
+    }
+
+    @Override
+    public void onBindViewHolder(NewTabPageListItemViewHolder holder, final int position) {
+        holder.onBindViewHolder(mNewTabPageListItems.get(position));
+    }
+
+    @Override
+    public int getItemCount() {
+        return mNewTabPageListItems.size();
+    }
+}