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/request_handler_unittest.cc

@@ -4,12 +4,12 @@
 
 #include <algorithm>
 #include <cmath>
+#include <memory>
 #include <sstream>
 #include <string>
 #include <vector>
 
-#include "include/base/cef_bind.h"
-#include "include/base/cef_scoped_ptr.h"
+#include "include/base/cef_callback.h"
 #include "include/cef_cookie.h"
 #include "include/cef_request_context_handler.h"
 #include "include/wrapper/cef_closure_task.h"
@@ -467,7 +467,7 @@ void RunNetNotifyTest(NetNotifyTestType test_type,
   for (size_t i = 0U; i < count; ++i) {
     CefRefPtr<NetNotifyTestHandler> handler =
         new NetNotifyTestHandler(&completion_state, test_type, same_origin);
-    collection.AddTestHandler(handler);
+    collection.AddTestHandler(handler.get());
     handlers.push_back(handler);
   }