Add an experimental standalone content suggestions UI.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
index 4d748070fe131c247518b1021d03560dd0d965fb..3299b3475d17f7421b75be266886590da408112e 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/NewTabPageAdapter.java
@@ -4,6 +4,7 @@
 
 package org.chromium.chrome.browser.ntp.cards;
 
+import android.support.annotation.Nullable;
 import android.support.v7.widget.RecyclerView;
 import android.support.v7.widget.RecyclerView.Adapter;
 import android.support.v7.widget.RecyclerView.ViewHolder;
@@ -27,32 +28,34 @@ import org.chromium.chrome.browser.offlinepages.OfflinePageBridge;
  */
 public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements NodeParent {
     private final NewTabPageManager mNewTabPageManager;
+    @Nullable
     private final View mAboveTheFoldView;
     private final UiConfig mUiConfig;
     private NewTabPageRecyclerView mRecyclerView;
 
     private final InnerNode mRoot;
 
-    private final AboveTheFoldItem mAboveTheFold = new AboveTheFoldItem();
+    @Nullable
+    private final AboveTheFoldItem mAboveTheFold;
     private final SectionList mSections;
     private final SignInPromo mSigninPromo;
     private final AllDismissedItem mAllDismissed;
     private final Footer mFooter;
-    private final SpacingItem mBottomSpacer = new SpacingItem();
+    private final SpacingItem mBottomSpacer;
 
     /**
      * Creates the adapter that will manage all the cards to display on the NTP.
      *
      * @param manager the NewTabPageManager to use to interact with the rest of the system.
      * @param aboveTheFoldView the layout encapsulating all the above-the-fold elements
-     *                         (logo, search box, most visited tiles)
+     *         (logo, search box, most visited tiles), or null if only suggestions should
+     *         be displayed.
      * @param uiConfig the NTP UI configuration, to be passed to created views.
      * @param offlinePageBridge the OfflinePageBridge used to determine if articles are available
-     *                              offline.
-     *
+     *         offline.
      */
-    public NewTabPageAdapter(NewTabPageManager manager, View aboveTheFoldView, UiConfig uiConfig,
-            OfflinePageBridge offlinePageBridge) {
+    public NewTabPageAdapter(NewTabPageManager manager, @Nullable View aboveTheFoldView,
+            UiConfig uiConfig, OfflinePageBridge offlinePageBridge) {
         mNewTabPageManager = manager;
         mAboveTheFoldView = aboveTheFoldView;
         mUiConfig = uiConfig;
@@ -63,8 +66,19 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
         mAllDismissed = new AllDismissedItem();
         mFooter = new Footer();
 
-        mRoot.addChildren(
-                mAboveTheFold, mSections, mSigninPromo, mAllDismissed, mFooter, mBottomSpacer);
+        if (mAboveTheFoldView == null) {
+            mAboveTheFold = null;
+        } else {
+            mAboveTheFold = new AboveTheFoldItem();
+            mRoot.addChild(mAboveTheFold);
+        }
+        mRoot.addChildren(mSections, mSigninPromo, mAllDismissed, mFooter);
+        if (mAboveTheFoldView == null) {
+            mBottomSpacer = null;
+        } else {
+            mBottomSpacer = new SpacingItem();
+            mRoot.addChild(mBottomSpacer);
+        }
 
         updateAllDismissedVisibility();
         mRoot.setParent(this);
@@ -127,6 +141,8 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     }
 
     public int getAboveTheFoldPosition() {
+        if (mAboveTheFoldView == null) return RecyclerView.NO_POSITION;
+
         return getChildPositionOffset(mAboveTheFold);
     }
 
@@ -146,6 +162,8 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     }
 
     int getBottomSpacerPosition() {
+        if (mBottomSpacer == null) return RecyclerView.NO_POSITION;
+
         return getChildPositionOffset(mBottomSpacer);
     }
 
@@ -165,7 +183,7 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     public void onItemRangeInserted(TreeNode child, int itemPosition, int itemCount) {
         assert child == mRoot;
         notifyItemRangeInserted(itemPosition, itemCount);
-        mBottomSpacer.refresh();
+        if (mBottomSpacer != null) mBottomSpacer.refresh();
 
         updateAllDismissedVisibility();
     }
@@ -174,7 +192,7 @@ public class NewTabPageAdapter extends Adapter<NewTabPageViewHolder> implements
     public void onItemRangeRemoved(TreeNode child, int itemPosition, int itemCount) {
         assert child == mRoot;
         notifyItemRangeRemoved(itemPosition, itemCount);
-        mBottomSpacer.refresh();
+        if (mBottomSpacer != null) mBottomSpacer.refresh();
 
         updateAllDismissedVisibility();
     }