macOS: Load the CEF framework using dlopen instead of direct linking (issue #2459)

This is a prerequisite for using the Chromium V2 sandbox.

tests/cefsimple/process_helper_mac.cc

@@ -3,9 +3,16 @@
 // be found in the LICENSE file.
 
 #include "include/cef_app.h"
+#include "include/wrapper/cef_library_loader.h"
 
 // Entry point function for sub-processes.
 int main(int argc, char* argv[]) {
+  // Load the CEF framework library at runtime instead of linking directly
+  // as required by the macOS sandbox implementation.
+  CefScopedLibraryLoader library_loader;
+  if (!library_loader.LoadInHelper())
+    return 1;
+
   // Provide CEF with command-line arguments.
   CefMainArgs main_args(argc, argv);