chrome: Improve positioning of dialogs (fixes #3628)

Dialogs will be excluded from regions near the top of the window
that contain overlays, draggable regions or titlebar.

libcef/browser/browser_platform_delegate.cc

@@ -264,9 +264,6 @@ std::unique_ptr<CefMenuRunner> CefBrowserPlatformDelegate::CreateMenuRunner() {
   return nullptr;
 }
 
-void CefBrowserPlatformDelegate::UpdateFindBarBoundingBox(
-    gfx::Rect* bounds) const {}
-
 bool CefBrowserPlatformDelegate::IsWindowless() const {
   return false;
 }