[ios] Fix DCHECK in currentURLWithTrustLevel for NTP.

Special case trusted currentURLWithTrustLevel URLs that have been
rewritten to return the URL, and not the virtual URL. This fixes a
DCHECK when navigating forward from the NTP to an internal page.

Bug: 925776
Change-Id: I8d23b79eecd2f5902c726c7e2d8f9878969b9364
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1778962
Auto-Submit: Justin Cohen <justincohen@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Eugene But <eugenebut@chromium.org>
Cr-Commit-Position: refs/heads/master@{#693213}

ios/web/web_state/ui/crw_web_controller.mm

@@ -667,7 +667,16 @@ typedef void (^ViewportStateCompletion)(const web::PageViewportState*);
   web::NavigationItem* item =
       self.navigationManagerImpl
           ->GetLastCommittedItemInCurrentOrRestoredSession();
-  return item ? item->GetVirtualURL() : GURL::EmptyGURL();
+  if (item) {
+    // This special case is added for any app specific URLs that have been
+    // rewritten to about:// URLs.
+    if (item->GetURL().SchemeIs(url::kAboutScheme) &&
+        web::GetWebClient()->IsAppSpecificURL(item->GetVirtualURL())) {
+      return item->GetURL();
+    }
+    return item->GetVirtualURL();
+  }
+  return GURL::EmptyGURL();
 }
 
 - (void)reloadWithRendererInitiatedNavigation:(BOOL)rendererInitiated {