The heads up now have a margin on top and don't stick to the edge

Bug: 21337754
Change-Id: I199bc0732df62eadc2458db12a7c1059da988020
diff --git a/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java b/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
index 081a9c5..5c604b6 100644
--- a/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
+++ b/packages/SystemUI/src/com/android/systemui/statusbar/stack/StackScrollAlgorithm.java
@@ -64,6 +64,7 @@
     private int mTopStackTotalSize;
     private int mPaddingBetweenElementsDimmed;
     private int mPaddingBetweenElementsNormal;
+    private int mNotificationsTopPadding;
     private int mBottomStackSlowDownLength;
     private int mTopStackSlowDownLength;
     private int mCollapseSecondCardPadding;
@@ -104,6 +105,8 @@
                 .getDimensionPixelSize(R.dimen.notification_padding_dimmed);
         mPaddingBetweenElementsNormal = context.getResources()
                 .getDimensionPixelSize(R.dimen.notification_padding);
+        mNotificationsTopPadding = context.getResources()
+                .getDimensionPixelSize(R.dimen.notifications_top_padding);
         mCollapsedSize = context.getResources()
                 .getDimensionPixelSize(R.dimen.notification_min_height);
         mMaxNotificationHeight = context.getResources()
@@ -518,7 +521,8 @@
                         bottomPosition);
             }
             if (row.isPinned()) {
-                childState.yTranslation = Math.max(childState.yTranslation, 0);
+                childState.yTranslation = Math.max(childState.yTranslation,
+                        mNotificationsTopPadding);
                 childState.height = row.getHeadsUpHeight();
                 if (!isTopEntry) {
                     // Ensure that a headsUp doesn't vertically extend further than the heads-up at