Add experimental code behind a flag for Content Size Policy

content/browser/web_contents/web_contents_impl.h

Index: content/browser/web_contents/web_contents_impl.h
diff --git a/content/browser/web_contents/web_contents_impl.h b/content/browser/web_contents/web_contents_impl.h
index 91226f87578512b1516706f852f25c009a18c5af..a3735106fc89836d76aa01c313104607a1b21ba2 100644
--- a/content/browser/web_contents/web_contents_impl.h
+++ b/content/browser/web_contents/web_contents_impl.h
@@ -751,6 +751,10 @@ class CONTENT_EXPORT WebContentsImpl
     return media_web_contents_observer_.get();
   }
 
+  LoaderIOThreadNotifier* loader_io_thread_notifier() {
+    return loader_io_thread_notifier_.get();
+  }
+
   // Update the web contents visibility.
   void UpdateWebContentsVisibility(bool visible);