Use DownloadManager to download non-html res when download icon pressed

chrome/browser/android/offline_pages/offline_page_utils.cc

 // Copyright 2015 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 "chrome/browser/android/offline_pages/offline_page_utils.h"
 
 #include "base/bind.h"
 #include "base/location.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
@@ skipping 11 matching lines @@
 #include "components/offline_pages/core/background/save_page_request.h"
 #include "components/offline_pages/core/client_namespace_constants.h"
 #include "components/offline_pages/core/client_policy_controller.h"
 #include "components/offline_pages/core/offline_page_feature.h"
 #include "components/offline_pages/core/offline_page_item.h"
 #include "components/offline_pages/core/offline_page_model.h"
 #include "components/offline_pages/core/request_header/offline_page_header.h"
 #include "content/public/browser/browser_context.h"
 #include "content/public/browser/navigation_entry.h"
 #include "content/public/browser/web_contents.h"
+#include "net/base/mime_util.h"
 
 namespace offline_pages {
 namespace {
 
 void OnGetPagesByURLDone(
     const GURL& url,
     int tab_id,
     const std::vector<std::string>& namespaces_to_show_in_original_tab,
     const base::Callback<void(const OfflinePageItem*)>& callback,
     const MultipleOfflinePageItemResult& pages) {
@@ skipping 249 matching lines @@
                                         DownloadUIActionFlags ui_action) {
   DCHECK(web_contents);
 
   OfflinePageTabHelper* tab_helper =
       OfflinePageTabHelper::FromWebContents(web_contents);
   if (!tab_helper)
     return;
   tab_helper->ScheduleDownloadHelper(web_contents, name_space, url, ui_action);
 }
 
+// static
+bool OfflinePageUtils::CanDownloadAsOfflinePage(
+    const GURL& url,
+    const std::string& contents_mime_type) {
+  return url.SchemeIsHTTPOrHTTPS() &&
+         (net::MatchesMimeType(contents_mime_type, "text/html") ||
+          net::MatchesMimeType(contents_mime_type, "application/xhtml+xml"));
+}
+
 }  // namespace offline_pages