Implement "pinned" mode in ash.

ash/common/wm_shell.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef ASH_COMMON_WM_SHELL_H_
 #define ASH_COMMON_WM_SHELL_H_
 
 #include <stdint.h>
 
 #include <memory>
@@ skipping 68 matching lines @@
   virtual bool IsForceMaximizeOnFirstRun() = 0;
 
   // Returns true if a system-modal dialog window is currently open.
   bool IsSystemModalWindowOpen();
 
   // For testing only: set simulation that a modal window is open
   void SimulateModalWindowOpenForTesting(bool modal_window_open) {
     simulate_modal_window_open_for_testing_ = modal_window_open;
   }
 
+  // Returns true if a window is currently pinned.
+  virtual bool IsPinned() = 0;
+
+  // Sets/Unsets the |window| to as a pinned window. If this is called with a
+  // window with WINDOW_STATE_TYPE_PINNED state, then this sets the |window|
+  // as a pinned window. Otherwise, this unsets it.
+  // For setting, a caller needs to guarantee that no windows are set
+  // as pinned window. For unsetting, a caller needs to guarantee that the
+  // |window| is the one which is currently set as a pinned window via previous
+  // this function invocation.
+  virtual void SetPinnedWindow(WmWindow* window) = 0;
+
   // Returns true if |window| can be shown for the current user. This is
   // intended to check if the current user matches the user associated with
   // |window|.
   // TODO(jamescook): Remove this when ShellDelegate is accessible via this
   // interface.
   virtual bool CanShowWindowForUser(WmWindow* window) = 0;
 
   // See aura::client::CursorClient for details on these.
   virtual void LockCursor() = 0;
   virtual void UnlockCursor() = 0;
@@ skipping 27 matching lines @@
 
   virtual void AddActivationObserver(WmActivationObserver* observer) = 0;
   virtual void RemoveActivationObserver(WmActivationObserver* observer) = 0;
 
   virtual void AddDisplayObserver(WmDisplayObserver* observer) = 0;
   virtual void RemoveDisplayObserver(WmDisplayObserver* observer) = 0;
 
   virtual void AddShellObserver(ShellObserver* observer) = 0;
   virtual void RemoveShellObserver(ShellObserver* observer) = 0;
 
-  // Notifies |observers_| when entering or exiting pinned mode for
-  // |pinned_window|. Entering or exiting can be checked by looking at
-  // |pinned_window|'s window state.
-  virtual void NotifyPinnedStateChanged(WmWindow* pinned_window) = 0;
-
  protected:
   WmShell();
   virtual ~WmShell();
 
   // If |delegate| is not null, sets and initializes the delegate. If |delegate|
   // is null, shuts down and destroys the delegate.
   void SetSystemTrayDelegate(std::unique_ptr<SystemTrayDelegate> delegate);
 
  private:
   friend class Shell;
 
   static WmShell* instance_;
 
   std::unique_ptr<FocusCycler> focus_cycler_;
   std::unique_ptr<WmSystemTrayNotifier> system_tray_notifier_;
   std::unique_ptr<SystemTrayDelegate> system_tray_delegate_;
 
   bool simulate_modal_window_open_for_testing_ = false;
 };
 
 }  // namespace ash
 
 #endif  // ASH_COMMON_WM_SHELL_H_