fix: use context counter as contextId (backport 3-0-x)

For sandboxed renderer it may not have a node::Environment in the context,
using a increasing counter as contextId works for all cases.

atom/renderer/atom_renderer_client.cc

@@ -79,6 +79,8 @@ void AtomRendererClient::RunScriptsAtDocumentEnd(
 void AtomRendererClient::DidCreateScriptContext(
     v8::Handle<v8::Context> context,
     content::RenderFrame* render_frame) {
+  RendererClientBase::DidCreateScriptContext(context, render_frame);
+
   // Only allow node integration for the main frame, unless it is a devtools
   // extension page.
   if (!render_frame->IsMainFrame() && !IsDevToolsExtension(render_frame))