Implement "pinned" mode in ash.

ash/mus/bridge/wm_shell_mus.cc

 // 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.
 
 #include "ash/mus/bridge/wm_shell_mus.h"
 
 #include "ash/common/default_accessibility_delegate.h"
 #include "ash/common/session/session_state_delegate.h"
 #include "ash/common/shell_observer.h"
 #include "ash/common/shell_window_ids.h"
@@ skipping 164 matching lines @@
 WmWindow* WmShellMus::GetRootWindowForNewWindows() {
   NOTIMPLEMENTED();
   return root_window_controllers_[0]->GetWindow();
 }
 
 bool WmShellMus::IsForceMaximizeOnFirstRun() {
   NOTIMPLEMENTED();
   return false;
 }
 
+bool WmShellMus::IsPinned() {
+  NOTIMPLEMENTED();
+  return false;
+}
+
 bool WmShellMus::CanShowWindowForUser(WmWindow* window) {
   NOTIMPLEMENTED();
   return true;
 }
 
 void WmShellMus::LockCursor() {
   NOTIMPLEMENTED();
 }
 
 void WmShellMus::UnlockCursor() {
@@ skipping 100 matching lines @@
                     OnWindowActivated(gained_active, lost_active));
 }
 
 void WmShellMus::OnWillDestroyClient(::mus::WindowTreeClient* client) {
   DCHECK_EQ(client, client_);
   RemoveClientObserver();
 }
 
 }  // namespace mus
 }  // namespace ash