Add ShelfWindowWatcher support for pre-existing windows.

ash/common/shelf/shelf_window_watcher.cc

 // Copyright 2013 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/common/shelf/shelf_window_watcher.h"
 
 #include <memory>
 #include <utility>
 
 #include "ash/common/shelf/shelf_constants.h"
@@ skipping 100 matching lines @@
 
 ////////////////////////////////////////////////////////////////////////////////
 
 ShelfWindowWatcher::ShelfWindowWatcher(ShelfModel* model)
     : model_(model),
       container_window_observer_(this),
       user_window_observer_(this),
       observed_container_windows_(&container_window_observer_),
       observed_user_windows_(&user_window_observer_) {
   WmShell::Get()->AddActivationObserver(this);
-  for (WmWindow* root : WmShell::Get()->GetAllRootWindows()) {
-    observed_container_windows_.Add(
-        root->GetChildByShellWindowId(kShellWindowId_DefaultContainer));
-    observed_container_windows_.Add(
-        root->GetChildByShellWindowId(kShellWindowId_PanelContainer));
-  }
-
+  for (const auto& display : display::Screen::GetScreen()->GetAllDisplays())
+    OnDisplayAdded(display);
   display::Screen::GetScreen()->AddObserver(this);
 }
 
 ShelfWindowWatcher::~ShelfWindowWatcher() {
   display::Screen::GetScreen()->RemoveObserver(this);
   WmShell::Get()->RemoveActivationObserver(this);
 }
 
 void ShelfWindowWatcher::AddShelfItem(WmWindow* window) {
   user_windows_with_items_.insert(window);
@@ skipping 73 matching lines @@
                                            WmWindow* lost_active) {
   if (gained_active && user_windows_with_items_.count(gained_active) > 0)
     OnUserWindowPropertyChanged(gained_active);
   if (lost_active && user_windows_with_items_.count(lost_active) > 0)
     OnUserWindowPropertyChanged(lost_active);
 }
 
 void ShelfWindowWatcher::OnDisplayAdded(const display::Display& new_display) {
   WmWindow* root = WmShell::Get()->GetRootWindowForDisplayId(new_display.id());
 
-  // When the primary root window's display get removed, the existing root
-  // window is taken over by the new display and the observer is already set.
+  // When the primary root window's display is removed, the existing root window
+  // is taken over by the new display, and the observer is already set.
   WmWindow* default_container =
       root->GetChildByShellWindowId(kShellWindowId_DefaultContainer);
-  if (!observed_container_windows_.IsObserving(default_container))
+  if (!observed_container_windows_.IsObserving(default_container)) {
+    for (WmWindow* window : default_container->GetChildren())
+      OnUserWindowAdded(window);
     observed_container_windows_.Add(default_container);
+  }
   WmWindow* panel_container =
       root->GetChildByShellWindowId(kShellWindowId_PanelContainer);
-  if (!observed_container_windows_.IsObserving(panel_container))
+  if (!observed_container_windows_.IsObserving(panel_container)) {
+    for (WmWindow* window : panel_container->GetChildren())
+      OnUserWindowAdded(window);
     observed_container_windows_.Add(panel_container);
+  }
 }
 
 void ShelfWindowWatcher::OnDisplayRemoved(const display::Display& old_display) {
 }
 
 void ShelfWindowWatcher::OnDisplayMetricsChanged(const display::Display&,
                                                  uint32_t) {}
 
 }  // namespace ash