Don't show location bar in bookmark apps if there has been no navigation

This prevents the location bar appearing and then disappearing when a
bookmark app is first opened.

BUG=463405

Review URL: https://codereview.chromium.org/1028503002

Cr-Commit-Position: refs/heads/master@{#321964}

chrome/browser/extensions/extension_ui_util.cc

@@ -79,6 +79,10 @@ bool ShouldShowLocationBar(const Extension* extension,
   if (!extension->from_bookmark())
     return false;
 
+  // Don't show a location bar until a navigation has occurred.
+  if (web_contents->GetLastCommittedURL().is_empty())
+    return false;
+
   GURL launch_url = AppLaunchInfo::GetLaunchWebURL(extension);
   return !(IsSameOriginOrMoreSecure(launch_url,
                                     web_contents->GetVisibleURL()) &&