Fix assert with distiller code caused by r419635.

components/dom_distiller/content/browser/dom_distiller_viewer_source.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/dom_distiller/content/browser/dom_distiller_viewer_source.h"
 
 #include <memory>
 #include <string>
 #include <utility>
 #include <vector>
@@ skipping 114 matching lines @@
   } else {
     DCHECK(buffer_.empty());
     if (web_contents()) {
       RunIsolatedJavaScript(web_contents()->GetMainFrame(), buffer);
     }
   }
 }
 
 void DomDistillerViewerSource::RequestViewerHandle::DidFinishNavigation(
     content::NavigationHandle* navigation_handle) {
+  if (!navigation_handle->IsInMainFrame() || !navigation_handle->HasCommitted())
+    return;
+
   const GURL& navigation = navigation_handle->GetURL();
   bool expected_main_view_request =
       navigation.SchemeIs(expected_scheme_.c_str()) &&
       expected_request_path_ == navigation.query();
   if (navigation_handle->IsSamePage() || expected_main_view_request) {
     // In-page navigations, as well as the main view request can be ignored.
     if (expected_main_view_request) {
       content::RenderFrameHost* render_frame_host =
           navigation_handle->GetRenderFrameHost();
       content::RenderViewHost* render_view_host =
@@ skipping 156 matching lines @@
 std::string DomDistillerViewerSource::GetContentSecurityPolicyStyleSrc()
     const {
   return "style-src 'self' https://fonts.googleapis.com;";
 }
 
 std::string DomDistillerViewerSource::GetContentSecurityPolicyChildSrc() const {
   return "child-src *;";
 }
 
 }  // namespace dom_distiller