Set article spacing in dp, not px.

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

Index: chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetItemDecoration.java
diff --git a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetItemDecoration.java b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetItemDecoration.java
index e7590a127ebfbda10365ba73f848266fadee88a6..ced483f6ea581d577953aa93b47b5ff37cf08981 100644
--- a/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetItemDecoration.java
+++ b/chrome/android/java/src/org/chromium/chrome/browser/ntp/snippets/SnippetItemDecoration.java
@@ -4,25 +4,82 @@
 
 package org.chromium.chrome.browser.ntp.snippets;
 
+import android.content.Context;
+import android.graphics.Canvas;
+import android.graphics.Paint;
 import android.graphics.Rect;
+import android.support.v4.content.ContextCompat;
 import android.support.v7.widget.RecyclerView;
+import android.support.v7.widget.RecyclerView.Adapter;
 import android.view.View;
 
+import org.chromium.chrome.R;
+import org.chromium.chrome.browser.ntp.cards.NewTabPageListItem;
+
 /**
- * A class that decorates the RecyclerView elements.
+ * A decorator that places separators between RecyclerView items of type
+ * {@value NewTabPageListItem#VIEW_TYPE_SNIPPET}.
  */
 public class SnippetItemDecoration extends RecyclerView.ItemDecoration {
-    private static final int VERTICAL_SPACE = 1;
+    private final int mVerticalSpace;
+    private final Paint mPaint = new Paint();
+
+    public SnippetItemDecoration(Context context) {
+        mVerticalSpace =
+                context.getResources().getDimensionPixelSize(R.dimen.snippets_vertical_spacing);
+        mPaint.setColor(ContextCompat.getColor(context, R.color.snippets_separator));
+    }
 
+    /**
+     * Add space between items to show the separator.

[Bernhard Bauer, 2016/05/09 11:21:56]

Nit: I would make this an implementation (non-Javadoc) comment (same for onDraw
below).

[PEConn, 2016/05/09 13:33:38]

Done.

+     */
     @Override
     public void getItemOffsets(Rect outRect, View view, RecyclerView parent,
             RecyclerView.State state) {
-        // Reset the bounds of the outRect.
-        outRect.setEmpty();
 
-        // Do not add a vertical space to the last item.
-        if (parent.getChildAdapterPosition(view) != parent.getAdapter().getItemCount() - 1) {
-            outRect.bottom = VERTICAL_SPACE;
+        if (shouldPlaceSeparator(view, parent)) {
+            // Reset the bounds of the outRect.
+            outRect.setEmpty();
+            outRect.bottom = mVerticalSpace;
         }
     }
+
+    /**
+     * Draw the separators as simple rectangles underneath relevant items.
+     */
+    @Override
+    public void onDraw(Canvas c, RecyclerView parent, RecyclerView.State state) {
+        final int left = parent.getPaddingLeft();

[May, 2016/05/09 11:47:53]

Can you just create this as a drawable shape xml or do we really need it drawn
directly on the canvas?

[PEConn, 2016/05/09 13:33:38]

Done.

+        final int right = parent.getWidth() - parent.getPaddingRight();
+
+        for (int i = 0; i < parent.getChildCount(); i++) {
+            View child = parent.getChildAt(i);
+            if (shouldPlaceSeparator(child, parent)) {
+                final RecyclerView.LayoutParams params =
+                        (RecyclerView.LayoutParams) child.getLayoutParams();
+
+                final int top = child.getBottom() + params.bottomMargin;
+                final int bottom = top + mVerticalSpace;
+
+                c.drawRect(left, top, right, bottom, mPaint);
+            }
+        }
+    }
+
+    /**
+     * Checks whether there should be a separator below the given view in the RecyclerView. Current
+     * logic checks if the current view and next view show articles.
+     */
+    private boolean shouldPlaceSeparator(View view, RecyclerView parent) {
+        int childPos = parent.getChildAdapterPosition(view);
+        Adapter adapter = parent.getAdapter();
+
+        // Ensure we are not the last child.
+        if (childPos == adapter.getItemCount() - 1) {
+            return false;
+        }
+
+        return adapter.getItemViewType(childPos) == NewTabPageListItem.VIEW_TYPE_SNIPPET
+                && adapter.getItemViewType(childPos + 1) == NewTabPageListItem.VIEW_TYPE_SNIPPET;
+    }
 }