Plumb file system permission into WebviewGuest.

chrome/browser/guest_view/guest_view.h

Index: chrome/browser/guest_view/guest_view.h
diff --git a/chrome/browser/guest_view/guest_view.h b/chrome/browser/guest_view/guest_view.h
index 8afabce72e5802f8c398776eefe92eba4ad05795..557e7aaae06797fa02c70deaf8405396dd79cd57 100644
--- a/chrome/browser/guest_view/guest_view.h
+++ b/chrome/browser/guest_view/guest_view.h
@@ -6,6 +6,7 @@
 #define CHROME_BROWSER_GUEST_VIEW_GUEST_VIEW_H_
 
 #include "chrome/browser/guest_view/guest_view_base.h"
+#include "content/public/browser/render_frame_host.h"
 
 template <typename T>
 class GuestView : public GuestViewBase {
@@ -23,6 +24,17 @@ class GuestView : public GuestViewBase {
     return guest ? guest->As<T>() : NULL;
   }
 
+  static T* FromFrameID(int render_process_id, int render_frame_id) {
+    content::RenderFrameHost* render_frame_host =
+        content::RenderFrameHost::FromID(render_process_id, render_frame_id);
+    if (!render_frame_host) {
+      return NULL;
+    }
+    content::WebContents* web_contents =
+        content::WebContents::FromRenderFrameHost(render_frame_host);
+    return FromWebContents(web_contents);
+  }
+
   T* GetOpener() const {
     GuestViewBase* guest = GuestViewBase::GetOpener();
     if (!guest)