macOS: Add support for and enable the V2 sandbox (issue #2459)

The CEF_USE_SANDBOX define is now used on all platforms.

tests/cefsimple/process_helper_mac.cc

@@ -5,8 +5,22 @@
 #include "include/cef_app.h"
 #include "include/wrapper/cef_library_loader.h"
 
+// When generating projects with CMake the CEF_USE_SANDBOX value will be defined
+// automatically. Pass -DUSE_SANDBOX=OFF to the CMake command-line to disable
+// use of the sandbox.
+#if defined(CEF_USE_SANDBOX)
+#include "include/cef_sandbox_mac.h"
+#endif
+
 // Entry point function for sub-processes.
 int main(int argc, char* argv[]) {
+#if defined(CEF_USE_SANDBOX)
+  // Initialize the macOS sandbox for this helper process.
+  CefScopedSandboxContext sandbox_context;
+  if (!sandbox_context.Initialize(argc, argv))
+    return 1;
+#endif
+
   // Load the CEF framework library at runtime instead of linking directly
   // as required by the macOS sandbox implementation.
   CefScopedLibraryLoader library_loader;