A few minor changes to the chrome.downloads extension API

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 binding = require('binding').Binding.create('downloads');
 var downloadsInternal = require('binding').Binding.create(
     'downloadsInternal').generate();
 var eventBindings = require('event_bindings');
 
 eventBindings.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 isValidResult(result) {
+    if (result === undefined)
+      return false;
+    if (typeof(result) != 'object') {
+      console.error('Error: Invocation of form suggest(' + typeof(result) +
+                    ') doesn\'t match definition suggest({filename: string, ' +
+                    'conflictAction: string})');
+      return false;
+    } else if ((typeof(result.filename) != 'string') ||
+               (result.filename.length == 0)) {
+      console.error('Error: "filename" parameter to suggest() must be a ' +
+                    'non-empty string');
+      return false;
+    } else if ([undefined, 'uniquify', 'overwrite', 'prompt'].indexOf(
+                 result.conflictAction) < 0) {
+      console.error('Error: "conflictAction" parameter to suggest() must be ' +
+                    'one of undefined, "uniquify", "overwrite", "prompt"');
+      return false;
+    }
+    return 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.conflict_action == undefined) ||
-          (typeof(result.conflict_action) == 'string'))) {
+    if (isValidResult(result)) {
       downloadsInternal.determineFilename(
-          downloadId, result.filename, result.conflict_action || "");
+          downloadId, result.filename, result.conflictAction || "");
     } else {
       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;
   }
 });
 exports.binding = binding.generate();