Clear cursor when exiting window to avoid incorrect caching

ui/views/widget/desktop_aura/desktop_native_widget_aura.cc

Index: ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
diff --git a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
index ab0172815037c8057a4ba3aafedae93f2d6aed41..98952a7cf12d2971b5806c08cb0ed9f3e124f5bb 100644
--- a/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
+++ b/ui/views/widget/desktop_aura/desktop_native_widget_aura.cc
@@ -945,6 +945,15 @@ void DesktopNativeWidgetAura::OnMouseEvent(ui::MouseEvent* event) {
   if (tooltip_manager_.get())
     tooltip_manager_->UpdateTooltip();
   TooltipManagerAura::UpdateTooltipManagerForCapture(GetWidget());
+  // This is required because the cursor is a per-thread property on Windows
+  // (not a per-window). We don't respond to WM_SETCURSOR, but instead rely on
+  // the cursor_client to call ::SetCursor appropriately. If we don't clear
+  // the cursor on exiting the widget, then the next time, the cursor client
+  // will not call ::SetCursor appropriately because it will believe it's
+  // already set the cursor for the window (and there's a cursor client per

[sky, 2013/11/22 21:26:47]

Why does the cursor client think it's already set the cursor?

+  // created per window).
+  if (event->type() == ui::ET_MOUSE_EXITED)
+    cursor_client_->SetCursor(ui::kCursorNull);
   native_widget_delegate_->OnMouseEvent(event);
   // WARNING: we may have been deleted.
 }