Add a NOT_DRAWN window in between the root_window and its children.

ash/public/cpp/shell_window_ids.h

Index: ash/public/cpp/shell_window_ids.h
diff --git a/ash/public/cpp/shell_window_ids.h b/ash/public/cpp/shell_window_ids.h
index f5f1fc233e92a0b54e0131f505755786801fe6df..fda55cd0111d3ff1f7e9291ef1f32e2ab32f2d1c 100644
--- a/ash/public/cpp/shell_window_ids.h
+++ b/ash/public/cpp/shell_window_ids.h
@@ -105,37 +105,42 @@ const int32_t kShellWindowId_MouseCursorContainer = 23;
 // The topmost container, used for power off animation.
 const int32_t kShellWindowId_PowerButtonAnimationContainer = 24;
 
+// The delegate root container in between root window and its children, used for
+// screen rotation animation.
+const int32_t kShellWindowId_DelegateRootContainer = 25;
+
 const int32_t kShellWindowId_Min = 0;
 const int32_t kShellWindowId_Max = kShellWindowId_PowerButtonAnimationContainer;
 
 // A list of all the above valid container IDs. Add any new ID to this list.
 // This list is needed to validate we have no duplicate IDs.
 const int32_t kAllShellContainerIds[] = {
-  kShellWindowId_NonLockScreenContainersContainer,
-  kShellWindowId_LockScreenContainersContainer,
-  kShellWindowId_LockScreenRelatedContainersContainer,
-  kShellWindowId_UnparentedControlContainer,
-  kShellWindowId_WallpaperContainer,
-  kShellWindowId_VirtualKeyboardContainer,
-  kShellWindowId_DefaultContainer,
-  kShellWindowId_AlwaysOnTopContainer,
-  kShellWindowId_ShelfContainer,
-  kShellWindowId_ShelfBubbleContainer,
-  kShellWindowId_PanelContainer,
-  kShellWindowId_AppListContainer,
-  kShellWindowId_SystemModalContainer,
-  kShellWindowId_LockScreenWallpaperContainer,
-  kShellWindowId_LockScreenContainer,
-  kShellWindowId_LockSystemModalContainer,
-  kShellWindowId_StatusContainer,
-  kShellWindowId_ImeWindowParentContainer,
-  kShellWindowId_MenuContainer,
-  kShellWindowId_DragImageAndTooltipContainer,
-  kShellWindowId_SettingBubbleContainer,
-  kShellWindowId_OverlayContainer,
-  kShellWindowId_PhantomWindow,
-  kShellWindowId_MouseCursorContainer,
-  kShellWindowId_PowerButtonAnimationContainer,
+    kShellWindowId_NonLockScreenContainersContainer,
+    kShellWindowId_LockScreenContainersContainer,
+    kShellWindowId_LockScreenRelatedContainersContainer,
+    kShellWindowId_UnparentedControlContainer,
+    kShellWindowId_WallpaperContainer,
+    kShellWindowId_VirtualKeyboardContainer,
+    kShellWindowId_DefaultContainer,
+    kShellWindowId_AlwaysOnTopContainer,
+    kShellWindowId_ShelfContainer,
+    kShellWindowId_ShelfBubbleContainer,
+    kShellWindowId_PanelContainer,
+    kShellWindowId_AppListContainer,
+    kShellWindowId_SystemModalContainer,
+    kShellWindowId_LockScreenWallpaperContainer,
+    kShellWindowId_LockScreenContainer,
+    kShellWindowId_LockSystemModalContainer,
+    kShellWindowId_StatusContainer,
+    kShellWindowId_ImeWindowParentContainer,
+    kShellWindowId_MenuContainer,
+    kShellWindowId_DragImageAndTooltipContainer,
+    kShellWindowId_SettingBubbleContainer,
+    kShellWindowId_OverlayContainer,
+    kShellWindowId_PhantomWindow,
+    kShellWindowId_MouseCursorContainer,
+    kShellWindowId_PowerButtonAnimationContainer,
+    kShellWindowId_DelegateRootContainer,
 };
 
 // These are the list of container ids of containers which may contain windows