Enable V8 sandbox by default (fixes #3332)

When the V8 sandbox is enabled, ArrayBuffer backing stores must be
allocated inside the sandbox address space. This change introduces a new
CefV8Value::CreateArrayBufferWithCopy method that copies the memory
contents into the sandbox address space.

Enabling the V8 sandbox can have a performance impact, especially when
passing large ArrayBuffers from C++ code to the JS side. We have therefore
retained the old CefV8Value::CreateArrayBuffer method that references
external memory. However, this method can only be used if the V8 sandbox is
disabled at CEF/Chromium build time.

To disable the V8 sandbox add `v8_enable_sandbox=false` to
`GN_DEFINES` when building CEF/Chromium.

libcef_dll/wrapper/cef_message_router.cc

@@ -1070,11 +1070,15 @@ class CefMessageRouterRendererSideImpl : public CefMessageRouterRendererSide {
 
     CefRefPtr<CefV8Context> context = GetContextByID(context_id);
     if (context && info->success_callback && context->Enter()) {
-      CefRefPtr<cmru::BinaryValueABRCallback> release_callback =
-          new cmru::BinaryValueABRCallback(response);
-
-      CefRefPtr<CefV8Value> value = CefV8Value::CreateArrayBuffer(
-          response->GetData(), response->GetSize(), release_callback);
+      CefRefPtr<CefV8Value> value;
+#ifdef CEF_V8_ENABLE_SANDBOX
+      value = CefV8Value::CreateArrayBufferWithCopy(response->GetData(),
+                                                    response->GetSize());
+#else
+      value = CefV8Value::CreateArrayBuffer(
+          response->GetData(), response->GetSize(),
+          new cmru::BinaryValueABRCallback(response));
+#endif
 
       context->Exit();