Change NavigationEntry to use virtual URL in error pages for blocked navigations

content/browser/frame_host/navigation_controller_impl.cc

Index: content/browser/frame_host/navigation_controller_impl.cc
diff --git a/content/browser/frame_host/navigation_controller_impl.cc b/content/browser/frame_host/navigation_controller_impl.cc
index 1e0e55b71fc212027d87e08368f5815c83eb9acf..c133a633181190a019af936a93be4a607c757ae6 100644
--- a/content/browser/frame_host/navigation_controller_impl.cc
+++ b/content/browser/frame_host/navigation_controller_impl.cc
@@ -162,6 +162,26 @@ bool ShouldTreatNavigationAsReload(const NavigationEntry* entry) {
   return false;
 }
 
+// Returns true if the error code indicates an error condition that is not
+// recoverable or navigation is blocked. In such cases, session history
+// navigations to the same NavigationEntry should not attempt to load the
+// original URL.
+// TODO(nasko): Find a better way to distinguish blocked vs failed navigations,
+// as this is a very hacky way of accomplishing this. For now, a handful of
+// error codes are considered, which are more or less known to be cases of
+// blocked navigations.
+bool IsBlockedNavigation(net::Error error_code) {
+  switch (error_code) {
+    case net::ERR_BLOCKED_BY_CLIENT:
+    case net::ERR_BLOCKED_BY_RESPONSE:
+    case net::ERR_BLOCKED_BY_XSS_AUDITOR:
+    case net::ERR_UNSAFE_REDIRECT:
+      return true;
+    default:
+      return false;
+  }
+}
+
 }  // namespace
 
 // NavigationControllerImpl ----------------------------------------------------
@@ -933,6 +953,24 @@ bool NavigationControllerImpl::RendererDidNavigate(
     frame_entry->set_redirect_chain(params.redirects);
   }
 
+  // When a navigation in the main frame is blocked, it will display an error
+  // page. To avoid loading the blocked URL on back/forward navigations,
+  // do not store it in the FrameNavigationEntry's URL or PageState. Instead,
+  // make it visible to the user as the virtual URL. Store a safe URL
+  // (about:blank) as the one to load if the entry is revisited.
+  // TODO(nasko): Consider supporting similar behavior for subframe
+  // navigations, including AUTO_SUBFRAME.
+  if (!rfh->GetParent() &&
+      IsBlockedNavigation(navigation_handle->GetNetErrorCode())) {
+    DCHECK(params.url_is_unreachable);
+    active_entry->SetURL(GURL(url::kAboutBlankURL));
+    active_entry->SetVirtualURL(params.url);
+    if (frame_entry) {
+      frame_entry->SetPageState(
+          PageState::CreateFromURL(active_entry->GetURL()));
+    }
+  }
+
   // Use histogram to track memory impact of redirect chain because it's now
   // not cleared for committed entries.
   size_t redirect_chain_size = 0;