Open/save dialog assumes the defaultPath parameter without '/' as a default file name.

chrome/browser/resources/file_manager/js/file_manager.js

 // Copyright (c) 2012 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.
 
 /**
  * FileManager constructor.
  *
  * FileManager objects encapsulate the functionality of the file selector
  * dialogs, as well as the full screen file manager application (though the
  * latter is not yet implemented).
  *
  * @constructor
  * @param {HTMLElement} dialogDom The DOM node containing the prototypical
  *     dialog UI.
  */
 function FileManager(dialogDom) {
   this.dialogDom_ = dialogDom;
   this.filesystem_ = null;
   this.params_ = location.search ?
                  JSON.parse(decodeURIComponent(location.search.substr(1))) :
                  {};
-  if (this.params_.defaultPath && this.params_.defaultPath.indexOf('/') != 0)

[dgozman, 2012/07/02 12:38:47]

Sometimes save-as dialog is called with 'drive/folder/file.name' as a parameter,
and this will break it.

-    this.params_.defaultPath = '/' + this.params_.defaultPath;
-
   this.listType_ = null;
   this.showDelayTimeout_ = null;
 
   this.selection = null;
 
   this.butterTimer_ = null;
   this.currentButter_ = null;
   this.butterLastShowTime_ = 0;
 
   this.filesystemObserverId_ = null;
@@ skipping 1032 matching lines @@
   FileManager.prototype.canExecute_ = function(commandId) {
     var readonly = this.isOnReadonlyDirectory();
     switch (commandId) {
       case 'copy':
       case 'cut':
         return this.document_.queryCommandEnabled(commandId);
 
       // Hack goes below, since we don't receive beforepaste event, but receive
       // beforecut and beforecopy events.
       case 'paste':
-        return this.isRenamingInProgress()
-                   ? this.document_.queryCommandEnabled(commandId)
-                   : (!!this.fileTransferController_ &&
-                      this.fileTransferController_.queryPasteCommandEnabled());
+        return this.isRenamingInProgress() ?
+                   this.document_.queryCommandEnabled(commandId) :
+                   (!!this.fileTransferController_ &&
+                    this.fileTransferController_.queryPasteCommandEnabled());
 
       case 'rename':
         return (// Initialized to the point where we have a current directory
                 !readonly &&
                 // Rename not in progress.
                 !this.isRenamingInProgress() &&
                 // Only one file selected.
                 this.selection &&
                 this.selection.totalCount == 1);
 
       case 'delete':
-        return (this.isRenamingInProgress()
-                ? this.document_.queryCommandEnabled(commandId)
-                : !readonly &&
-                  this.selection &&
-                  this.selection.totalCount > 0);
+        return (this.isRenamingInProgress() ?
+                this.document_.queryCommandEnabled(commandId) :
+                !readonly &&
+                    this.selection &&
+                    this.selection.totalCount > 0);
 
       case 'newfolder':
         return !readonly &&
                !this.directoryModel_.isSearching() &&
                (this.dialogType_ == FileManager.DialogType.SELECT_SAVEAS_FILE ||
                 this.dialogType_ == FileManager.DialogType.FULL_PAGE);
 
       case 'unmount':
         return true;
 
@@ skipping 370 matching lines @@
    */
   FileManager.prototype.setupCurrentDirectory_ = function(pageLoading) {
     var path = location.hash ?  // Location hash has the highest priority.
         decodeURI(location.hash.substr(1)) :
         this.params_.defaultPath;
 
     if (!pageLoading && path == this.directoryModel_.getCurrentDirPath())
       return;
 
     if (!path) {
-      this.directoryModel_.setupDefaultPath();
-      return;
+      path = this.directoryModel_.getDefaultDirectory();
+    } else if (path.indexOf('/') == -1) {
+      // Path is a file name.
+      path = this.directoryModel_.getDefaultDirectory() + '/' + path;
     }
 
     // In the FULL_PAGE mode if the hash path points to a file we might have
     // to invoke a task after selecting it.
     // If the file path is in params_ we only want to select the file.
     var invokeHandlers = pageLoading && !this.params_.selectOnly &&
         this.dialogType_ == FileManager.DialogType.FULL_PAGE &&
         !!location.hash;
 
     if (DirectoryModel.getRootType(path) == DirectoryModel.RootType.GDATA) {
@@ skipping 3084 matching lines @@
     function closeBanner() {
       self.cleanupGDataWelcome_();
       // Stop showing the welcome banner.
       localStorage[WELCOME_HEADER_COUNTER_KEY] = WELCOME_HEADER_COUNTER_LIMIT;
     }
 
     return maybeShowBanner;
   };
 })();