Makes ScreenPinningController clear map after removing observers

ash/common/wm/workspace/workspace_layout_manager.cc

Index: ash/common/wm/workspace/workspace_layout_manager.cc
diff --git a/ash/common/wm/workspace/workspace_layout_manager.cc b/ash/common/wm/workspace/workspace_layout_manager.cc
index 6ccf018160184e386fdf2d5cdeac5fdae58f91d7..8ae1e3fe6aebf390f04556d6a80b339c5bd32a0a 100644
--- a/ash/common/wm/workspace/workspace_layout_manager.cc
+++ b/ash/common/wm/workspace/workspace_layout_manager.cc
@@ -320,7 +320,8 @@ void WorkspaceLayoutManager::OnFullscreenStateChanged(bool is_fullscreen,
 }
 
 void WorkspaceLayoutManager::OnPinnedStateChanged(WmWindow* pinned_window) {
-  if (!WmShell::Get()->IsPinned() && is_fullscreen_) {
+  const bool is_pinned = WmShell::Get()->IsPinned();
+  if (!is_pinned && is_fullscreen_) {
     // On exiting from pinned mode, if the workspace is still in fullscreen
     // mode, then this event does not trigger the restoring yet. On exiting
     // from fullscreen, the temporarily disabled always-on-top property will be
@@ -328,7 +329,7 @@ void WorkspaceLayoutManager::OnPinnedStateChanged(WmWindow* pinned_window) {
     return;
   }
 
-  UpdateAlwaysOnTop(WmShell::Get()->IsPinned() ? pinned_window : nullptr);
+  UpdateAlwaysOnTop(is_pinned ? pinned_window : nullptr);
 }
 
 void WorkspaceLayoutManager::OnVirtualKeyboardStateChanged(