Changes workspace code to only move windows when the work area changes

ash/wm/workspace/workspace_layout_manager2.h

Index: ash/wm/workspace/workspace_layout_manager2.h
diff --git a/ash/wm/workspace/workspace_layout_manager2.h b/ash/wm/workspace/workspace_layout_manager2.h
index 3c0e6ab4d5af5f76c915f4f78eec9d6f608408d5..1f35e04855ad420b9cd600f4855c42ddda1ed6bb 100644
--- a/ash/wm/workspace/workspace_layout_manager2.h
+++ b/ash/wm/workspace/workspace_layout_manager2.h
@@ -15,6 +15,7 @@
 #include "ui/aura/root_window_observer.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/aura/window_observer.h"
+#include "ui/gfx/rect.h"
 
 namespace aura {
 class RootWindow;
@@ -101,6 +102,10 @@ class ASH_EXPORT WorkspaceLayoutManager2
   // Set of windows we're listening to.
   WindowSet windows_;
 
+  // The work area. Cached to avoid unnecessarily moving windows during a
+  // workspace switch.
+  gfx::Rect work_area_;
+
   DISALLOW_COPY_AND_ASSIGN(WorkspaceLayoutManager2);
 };