[NTP Snippets] Fill space below the last snippet if necessary

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SpacingListItem.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SpacingListItem.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SpacingListItem.java
new file mode 100644
index 0000000000000000000000000000000000000000..8541fac8707b3a46d2d0d11d891b4997a453de45
--- /dev/null
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/cards/SpacingListItem.java
@@ -0,0 +1,39 @@
+// 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.cards;
+
+import android.content.Context;
+import android.view.View;
+import android.view.ViewGroup;
+
+/**
+ * Placeholder item to let the snippets flow to the top of the scroll list even when it does not
+ * contain enough of them. It is displayed as a dummy item with variable height that just occupies
+ * the remaining space between the last item in the RecyclerView and the bottom of the screen.
+ */
+public class SpacingListItem implements NewTabPageListItem {
+    private static class SpacingListItemView extends View {
+        public SpacingListItemView(Context context) {
+            super(context);
+        }
+
+        @Override
+        protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
+            assert getParent() instanceof NewTabPageRecyclerView;

[Bernhard Bauer, 2016/05/12 11:21:00]

You'll get an exception anyway if this isn't the case.

[dgn, 2016/05/13 13:49:59]

Removed.

+            setMeasuredDimension(
+                    0, ((NewTabPageRecyclerView) getParent()).calculateBottomSpacing());

[Bernhard Bauer, 2016/05/12 11:21:00]

So, stupid question: If all we are doing here is setting a height value that we
get from somewhere else anyway... couldn't we just set this as a minimum height
in advance?

[dgn, 2016/05/13 13:49:59]

The places where we manually request a recalculation (header being resized,
snippet being removed) are not enough to make sure it's always going to be the
right size. For example, when the padding is attached while the cards are being
pulled up following a dismissal. It's a null reference before that so the value
can't be set on it, it has to pull it itself instead.

+        }
+    }
+
+    /** Creates the View object for displaying the variable spacing. */
+    public static View createView(ViewGroup parent) {
+        return new SpacingListItemView(parent.getContext());
+    }
+
+    @Override
+    public int getType() {
+        return NewTabPageListItem.VIEW_TYPE_SPACING;
+    }
+}