exo: Clean up cursor code

components/exo/shell_surface.cc

 // Copyright 2015 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 "components/exo/shell_surface.h"
 
 #include <algorithm>
 
 #include "ash/common/frame/custom_frame_view_ash.h"
 #include "ash/common/shelf/wm_shelf.h"
@@ skipping 1291 matching lines @@
 
   aura::Window* window = GetDragWindow();
   if (!window || window->HasCapture())
     return;
 
   if (bounds_mode_ == BoundsMode::SHELL) {
     // Set the cursor before calling CreateWindowResizer(), as that will
     // eventually call LockCursor() and prevent the cursor from changing.
     aura::client::CursorClient* cursor_client =
         aura::client::GetCursorClient(window->GetRootWindow());
-    DCHECK(cursor_client);
+    if (!cursor_client)
+      return;
 
     switch (component) {
       case HTCAPTION:
         cursor_client->SetCursor(ui::kCursorPointer);
         break;
       case HTTOP:
         cursor_client->SetCursor(ui::kCursorNorthResize);
         break;
       case HTTOPRIGHT:
         cursor_client->SetCursor(ui::kCursorNorthEastResize);
@@ skipping 381 matching lines @@
 gfx::Point ShellSurface::GetMouseLocation() const {
   aura::Window* const root_window = widget_->GetNativeWindow()->GetRootWindow();
   gfx::Point location =
       root_window->GetHost()->dispatcher()->GetLastMouseLocationInRoot();
   aura::Window::ConvertPointToTarget(
       root_window, widget_->GetNativeWindow()->parent(), &location);
   return location;
 }
 
 }  // namespace exo