Grant access to files in PageState, which have already been validated.

content/browser/frame_host/render_frame_host_impl.cc

Index: content/browser/frame_host/render_frame_host_impl.cc
diff --git a/content/browser/frame_host/render_frame_host_impl.cc b/content/browser/frame_host/render_frame_host_impl.cc
index b1b2eb400d02fcd5a9e24badf3656c56998cdefb..d479a0fc7ab9bf1af2d968190328ab23dfa05dfc 100644
--- a/content/browser/frame_host/render_frame_host_impl.cc
+++ b/content/browser/frame_host/render_frame_host_impl.cc
@@ -1320,6 +1320,15 @@ void RenderFrameHostImpl::Navigate(const FrameMsg_Navigate_Params& params) {
     }
   }
 
+  // We may be returning to an existing NavigationEntry that had been granted
+  // file access.  If this is a different process, we will need to grant the
+  // access again.  The files listed in the page state are validated when they
+  // are received from the renderer to prevent abuse.
+  if (params.commit_params.page_state.IsValid()) {
+    render_view_host_->GrantFileAccessFromPageState(
+        params.commit_params.page_state);
+  }
+
   // Only send the message if we aren't suspended at the start of a cross-site
   // request.
   if (navigations_suspended_) {