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/temp_window_win.cc

@@ -16,7 +16,7 @@ const wchar_t kWndClass[] = L"Client_TempWindow";
 
 // Create the temp window.
 HWND CreateTempWindow() {
-  HINSTANCE hInstance = ::GetModuleHandle(NULL);
+  HINSTANCE hInstance = ::GetModuleHandle(nullptr);
 
   WNDCLASSEX wc = {0};
   wc.cbSize = sizeof(wc);
@@ -27,14 +27,14 @@ HWND CreateTempWindow() {
 
   // Create a 1x1 pixel hidden window.
   return CreateWindow(kWndClass, 0, WS_OVERLAPPEDWINDOW | WS_CLIPCHILDREN, 0, 0,
-                      1, 1, NULL, NULL, hInstance, NULL);
+                      1, 1, nullptr, nullptr, hInstance, nullptr);
 }
 
 TempWindowWin* g_temp_window = nullptr;
 
 }  // namespace
 
-TempWindowWin::TempWindowWin() : hwnd_(NULL) {
+TempWindowWin::TempWindowWin() : hwnd_(nullptr) {
   DCHECK(!g_temp_window);
   g_temp_window = this;