Fix UI bugs when dragging items

- On large devices, snap to next screen when you drag an item to the next screen (matches behavior on phones)
- Do not fade out outlines of Workspace pages while using spring loaded mode
- Keep all icons on all pages opaque in spring loaded mode
- Optimize call to clear a CellLayout

Change-Id: Ia15e0e9da499d7835a77218985de47a1f195e4ef

src/com/android/launcher2/CellLayout.java

@@ -661,8 +661,10 @@ public class CellLayout extends ViewGroup {
 
     @Override
     public void removeAllViewsInLayout() {
-        clearOccupiedCells();
-        mChildren.removeAllViewsInLayout();
+        if (mChildren.getChildCount() > 0) {
+            clearOccupiedCells();
+            mChildren.removeAllViewsInLayout();
+        }
     }
 
     public void removeViewWithoutMarkingCells(View view) {