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

chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/NewTabPageAdapter.java

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/NewTabPageAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/NewTabPageAdapter.java
new file mode 100644
index 0000000000000000000000000000000000000000..95d249796135d42dfb64c66481ac9adb34094a22
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/v2/NewTabPageAdapter.java
@@ -0,0 +1,104 @@
+// 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.v2;
+
+import android.support.v7.widget.RecyclerView.Adapter;
+import android.view.ViewGroup;
+
+import org.chromium.base.Log;
+import org.chromium.chrome.browser.ntp.NewTabPageLayout;
+import org.chromium.chrome.browser.ntp.NewTabPageView.NewTabPageManager;
+import org.chromium.chrome.browser.ntp.NewTabPageViewHolder;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticle;
+import org.chromium.chrome.browser.ntp.snippets.SnippetArticleViewHolder;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge;
+import org.chromium.chrome.browser.ntp.snippets.SnippetsBridge.SnippetsObserver;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/**
+ * A class that handles merging above the fold elements and below the fold cards into an adapter
+ * that will be used to back the NTP RecyclerView. The first element in the adapter should always be
+ * the above-the-fold view (containing the logo, search box, and most visited tiles) and subsequent
+ * elements will be the cards shown to the user
+ */
+public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements SnippetsObserver {
+    private static final String TAG = "Ntp";
+
+    private final NewTabPageManager mNewTabPageManager;
+    private final NewTabPageLayout mNewTabPageLayout;
+    private final AboveTheFoldListItem mAboveTheFoldListItem;
+    private final SnippetsBridge mSnippetsBridge;
+    private final List<NewTabPageListItem> mNewTabPageListItems;
+
+    /**
+     * Constructor to create the manager for all the cards to display on the NTP
+     *
+     * @param snippetsManager the NewTabPageManager to use to start navigations

[newt (away), 2016/03/30 19:03:51]

update params in javadoc

[dgn, 2016/03/31 00:46:45]

Done.

+     * @param newTabPageLayout the layout encapsulating all the above-the-fold elements
+     * (logo, search box, most visited tiles)
+     */
+    public NewTabPageAdapter(SnippetsBridge snippetsBridge, NewTabPageManager manager,
+            NewTabPageLayout newTabPageLayout) {
+        mNewTabPageManager = manager;
+        mNewTabPageLayout = newTabPageLayout;
+        mSnippetsBridge = snippetsBridge;
+        mAboveTheFoldListItem = new AboveTheFoldListItem();
+        mNewTabPageListItems = new ArrayList<NewTabPageListItem>();
+        mNewTabPageListItems.add(mAboveTheFoldListItem);
+
+        mSnippetsBridge.setObserver(this);

[newt (away), 2016/03/30 19:03:51]

Shouldn't we remove this observer? Or are you counting on the SnippetBridge
lifetime being the same as the NewTabPageAdapter? (That seems like a slightly
dangerous hidden assumption that could lead to a memory leak.)

[dgn, 2016/03/31 00:46:45]

Added methods to do it at NTP#destroy() time.

+    }
+
+    @Override
+    public void onSnippetsReceived(List<SnippetArticle> listSnippets) {
+        int newSnippetCount = listSnippets.size();
+        Log.d(TAG, "Received %d new snippets.", newSnippetCount);
+        mNewTabPageListItems.clear();
+        mNewTabPageListItems.add(mAboveTheFoldListItem);
+
+        if (newSnippetCount > 0) {
+            mNewTabPageListItems.add(new HeaderListItem());
+            mNewTabPageListItems.addAll(listSnippets);
+        }
+
+        notifyDataSetChanged();
+    }
+
+    @Override
+    @NewTabPageListItem.ViewType
+    public int getItemViewType(int position) {
+        return mNewTabPageListItems.get(position).getType();
+    }
+
+    @Override
+    public NewTabPageViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
+        if (viewType == NewTabPageListItem.VIEW_TYPE_ABOVE_THE_FOLD) {
+            return new AboveTheFoldListItem.ViewHolder(mNewTabPageLayout);
+        }
+
+        if (viewType == NewTabPageListItem.VIEW_TYPE_HEADER) {
+            return new HeaderListItem.ViewHolder(HeaderListItem.ViewHolder.createView(parent));
+        }
+
+        if (viewType == NewTabPageListItem.VIEW_TYPE_SNIPPET) {
+            return new SnippetArticleViewHolder(
+                    SnippetArticleViewHolder.createView(parent), mNewTabPageManager);
+        }
+
+        return null;
+    }
+
+    @Override
+    public void onBindViewHolder(NewTabPageViewHolder holder, final int position) {
+        holder.onBindViewHolder(mNewTabPageListItems.get(position));
+    }
+
+    @Override
+    public int getItemCount() {
+        return mNewTabPageListItems.size();
+    }
+}