Bug 1402481 - Reverse incorrect sign of margin calculation. r=mcomella

MozReview-Commit-ID: ICS81o8pLOE

--HG--
extra : rebase_source : 9ee338ea1726ff529a77af8a93ba5fda52caa698

mobile/android/base/java/org/mozilla/gecko/activitystream/homepanel/HighlightsDividerItemDecoration.java

@@ -61,7 +61,9 @@ import android.view.View;
 
             final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams) child
                     .getLayoutParams();
-            final int topOfDivider = child.getTop() + params.topMargin;
+            final int dividerHeight = divider.getIntrinsicHeight();
+            // Use dividerHeight / 2 to account for divider height and place it evenly between the two views.
+            final int topOfDivider = child.getTop() - params.topMargin - dividerHeight / 2;
             final int bottomOfDivider = topOfDivider + divider.getIntrinsicHeight();
             divider.setBounds(left, topOfDivider, right, bottomOfDivider);
             divider.draw(c);