Add |extra_info| parameter for browser creation (fixes issue #1088)

The optional |extra_info| parameter provides an opportunity to specify extra
information specific to the created browser that will be passed to
CefRenderProcessHandler::OnBrowserCreated() in the render process.

libcef/browser/browser_host_impl.h

@@ -135,6 +135,8 @@ class CefBrowserHostImpl : public CefBrowserHost,
     // request context will be used.
     CefRefPtr<CefRequestContext> request_context;
 
+    CefRefPtr<CefDictionaryValue> extra_info;
+
     // Used when explicitly creating the browser as an extension host via
     // ProcessManager::CreateBackgroundHost.
     const extensions::Extension* extension = nullptr;