Draw web content area correctly on a phantom window for window dragging

ash/wm/workspace/workspace_window_resizer.h

Index: ash/wm/workspace/workspace_window_resizer.h
diff --git a/ash/wm/workspace/workspace_window_resizer.h b/ash/wm/workspace/workspace_window_resizer.h
index 9667b7a41b700822db7c8a3df8848c3d299da267..c639c68df80dcd6dd48f66b819083c0fc4c19f81 100644
--- a/ash/wm/workspace/workspace_window_resizer.h
+++ b/ash/wm/workspace/workspace_window_resizer.h
@@ -16,6 +16,10 @@ namespace aura {
 class RootWindow;
 }  // namespace aura
 
+namespace ui {
+class Layer;
+}  // namespace ui
+
 namespace ash {
 namespace internal {
 
@@ -132,6 +136,9 @@ class ASH_EXPORT WorkspaceWindowResizer : public WindowResizer {
   // Returns true if we should allow the mouse pointer to warp.
   bool ShouldAllowMouseWarp() const;
 
+  // Recreates a fresh layer for window() and all its child windows.
+  void RecreateWindowLayers();
+
   aura::Window* window() const { return details_.window; }
 
   const Details details_;
@@ -186,6 +193,10 @@ class ASH_EXPORT WorkspaceWindowResizer : public WindowResizer {
   // The mouse location passed to Drag().
   gfx::Point last_mouse_location_;
 
+  // The copy of window()->layer() and its children. This object is the owner of
+  // the layer.
+  ui::Layer* layer_;
+
   DISALLOW_COPY_AND_ASSIGN(WorkspaceWindowResizer);
 };