Adding a gray semi transparent backdrop behind the topmost window within the default container

ash/wm/maximize_mode/maximize_mode_window_manager.h

Index: ash/wm/maximize_mode/maximize_mode_window_manager.h
diff --git a/ash/wm/maximize_mode/maximize_mode_window_manager.h b/ash/wm/maximize_mode/maximize_mode_window_manager.h
index 7b0c1db6e0e0766a22bcc06963a19f83c1238f2b..6a0439922723cabb816428ebee8790cfe81640dd 100644
--- a/ash/wm/maximize_mode/maximize_mode_window_manager.h
+++ b/ash/wm/maximize_mode/maximize_mode_window_manager.h
@@ -9,6 +9,7 @@
 #include <set>
 
 #include "ash/ash_export.h"
+#include "ash/shell_observer.h"
 #include "ash/wm/window_state.h"
 #include "base/basictypes.h"
 #include "base/compiler_specific.h"
@@ -27,14 +28,19 @@ namespace internal{
 // With the destruction of the manager all windows will be restored to their
 // original state.
 class ASH_EXPORT MaximizeModeWindowManager : public aura::WindowObserver,
-                                             public gfx::DisplayObserver {
+                                             public gfx::DisplayObserver,
+                                             public ShellObserver {
  public:
   // This should only be deleted by the creator (ash::Shell).
   virtual ~MaximizeModeWindowManager();
 
- // Returns the number of maximized & tracked windows by this manager.
+  // Returns the number of maximized & tracked windows by this manager.
   int GetNumberOfManagedWindows();
 
+  // Hide the default workspace container backdrops temporarily when |hide| is
+  // set.
+  void HideBackdrops(bool hide);

[sky, 2014/03/06 01:03:18]

Do you really need the 'hide' variable? If you do, name it is_temporary to make
it clear. And document what 'temporary' means here. I don't see the
implementation of these either.

[Mr4D (OOO till 08-26), 2014/03/06 17:17:16]

Removed.

+
   // Overridden from WindowObserver:
   virtual void OnWindowDestroying(aura::Window* window) OVERRIDE;
   virtual void OnWindowAdded(aura::Window* window) OVERRIDE;
@@ -48,6 +54,10 @@ class ASH_EXPORT MaximizeModeWindowManager : public aura::WindowObserver,
   virtual void OnDisplayAdded(const gfx::Display& display) OVERRIDE;
   virtual void OnDisplayRemoved(const gfx::Display& display) OVERRIDE;
 
+  // ShellObserver overrides:
+  void OnOverviewModeStarted();
+  void OnOverviewModeEnded();
+
  protected:
   friend class ash::Shell;
 
@@ -91,15 +101,24 @@ class ASH_EXPORT MaximizeModeWindowManager : public aura::WindowObserver,
   // Remove Window creation observers.
   void RemoveWindowCreationObservers();
 
+  // Add a backdrop behind the currently active window on each desktop.
+  void EnableBackdropBehindTopWindowOnEachDisplay(bool enable);
+
   // Returns true when the |window| is a container window.
   bool IsContainerWindow(aura::Window* window);
 
+  // Apply a display configuration change.
+  void DisplayConfigurationChanged();
+
   // Every window which got touched by our window manager gets added here.
   WindowToShowState initial_show_state_;
 
   // All container windows which have to be tracked.
   std::set<aura::Window*> observed_container_windows_;
 
+  // True if all backdrops are hidden.
+  bool backdrops_hidden_;
+
   DISALLOW_COPY_AND_ASSIGN(MaximizeModeWindowManager);
 };