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/ceftests/test_handler.h

@@ -8,11 +8,11 @@
 
 #include <list>
 #include <map>
+#include <memory>
 #include <string>
 #include <utility>
 
-#include "include/base/cef_bind.h"
-#include "include/base/cef_scoped_ptr.h"
+#include "include/base/cef_callback.h"
 #include "include/cef_browser.h"
 #include "include/cef_client.h"
 #include "include/cef_frame.h"
@@ -293,7 +293,7 @@ class TestHandler : public CefClient,
   bool destroy_test_expected_;
   bool destroy_test_called_;
 
-  scoped_ptr<UIThreadHelper> ui_thread_helper_;
+  std::unique_ptr<UIThreadHelper> ui_thread_helper_;
 
   // Used to track the number of currently existing browser windows.
   static int browser_count_;