Various fixes related to the C++11/14 update (see issue #3140)

- Convert scoped_ptr to std::unique_ptr from <memory>
- Convert arraysize to base::size from include/base/cef_cxx17_backports.h
- Convert NULL to nullptr
- Include include/base/cef_callback.h instead of include/base/cef_bind.h
- Implicit conversion of CefRefPtr<T> or scoped_refptr<T> to T* is gone;
  use .get() instead

See the issue for additional details.

tests/cefclient/browser/views_window.h

@@ -174,7 +174,8 @@ class ViewsWindow : public CefBrowserViewDelegate,
 
  private:
   // |delegate| is guaranteed to outlive this object.
-  // |browser_view| may be NULL, in which case SetBrowserView() will be called.
+  // |browser_view| may be nullptr, in which case SetBrowserView() will be
+  // called.
   ViewsWindow(Delegate* delegate, CefRefPtr<CefBrowserView> browser_view);
 
   void SetBrowserView(CefRefPtr<CefBrowserView> browser_view);