Simplify WorkAreaBounds access logic

ash/screen_ash.cc

Index: ash/screen_ash.cc
diff --git a/ash/screen_ash.cc b/ash/screen_ash.cc
index 8a5a08913e774dc6a36ff2ed1852515392c1bbfa..4c7e1db3f48c260bebbb97b0ba6e713e5c54e702 100644
--- a/ash/screen_ash.cc
+++ b/ash/screen_ash.cc
@@ -40,21 +40,12 @@ gfx::Display ScreenAsh::FindDisplayContainingPoint(const gfx::Point& point) {
 // static
 gfx::Rect ScreenAsh::GetMaximizedWindowBoundsInParent(aura::Window* window) {
   if (window->GetRootWindow() == Shell::GetPrimaryRootWindow())
-    return Shell::GetInstance()->shelf()->GetMaximizedWindowBounds(window);
+    return GetDisplayWorkAreaBoundsInParent(window);
   else
     return GetDisplayBoundsInParent(window);
 }
 
 // static
-gfx::Rect ScreenAsh::GetUnmaximizedWorkAreaBoundsInParent(
-    aura::Window* window) {
-  if (window->GetRootWindow() == Shell::GetPrimaryRootWindow())
-    return Shell::GetInstance()->shelf()->GetUnmaximizedWorkAreaBounds(window);
-  else
-    return GetDisplayWorkAreaBoundsInParent(window);
-}
-
-// static
 gfx::Rect ScreenAsh::GetDisplayBoundsInParent(aura::Window* window) {
   return ConvertRectFromScreen(
       window->parent(),