Implement chrome.downloads.onDeterminingFilename()

chrome/renderer/resources/extensions/downloads_custom_bindings.js

+// Copyright (c) 2013 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.
+
+// Custom bindings for the downloads API.
+
+var chromeHidden = requireNative('chrome_hidden').GetChromeHidden();
+
+chromeHidden.Event.registerArgumentMassager(
+    'downloads.onDeterminingFilename',
+    function massage_determining_filename(args, dispatch) {
+  var downloadItem = args[0];
+  // Copy the id so that extensions can't change it.
+  var downloadId = downloadItem.id;
+  var suggestable = true;
+  function suggestCallback(result) {
+    if (!suggestable) {
+      console.error('suggestCallback may not be called more than once.');
+      return;
+    }
+    suggestable = false;
+    if ((typeof(result) == 'object') &&
+        result.filename &&
+        (typeof(result.filename) == 'string') &&
+        ((result.overwrite === undefined) ||
+          (typeof(result.overwrite) == 'boolean'))) {
+      chromeHidden.internalAPIs.downloadsInternal.determineFilename(
+          downloadId,
+          result.filename,
+          result.overwrite || false);
+    } else {
+      chromeHidden.internalAPIs.downloadsInternal.determineFilename(
+          downloadId);
+    }
+  }
+  try {
+    var results = dispatch([downloadItem, suggestCallback]);
+    var async = (results &&
+                 results.results &&
+                 (results.results.length != 0) &&
+                 (results.results[0] === true));
+    if (suggestable && !async)
+      suggestCallback();
+  } catch (e) {
+    suggestCallback();
+    throw e;
+  }
+});