[filemanager] Open Downloads by default (instead of removable device).

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).
@@ skipping 2694 matching lines @@
             // This device mount was the reason this File Manager instance was
             // created. Now the device is unmounted from another instance
             // or the user removed the device manually. Close this instance.
             // window.close() sometimes doesn't work.
             chrome.tabs.getCurrent(function(tab) {
               chrome.tabs.remove(tab.id);
             });
             return;
           }
           // Current directory just unmounted. Move to the 'Downloads'.
-          changeDirectoryTo = '/' + DirectoryModel.DOWNLOADS_DIRECTORY;
+          changeDirectoryTo = this.directoryModel_.getDefaultDirectory();
         }
       }
 
       // Even if something failed root list should be rescanned.
       // Failed mounts can "give" us new devices which might be formatted,
       // so we have to refresh root list then.
       self.directoryModel_.updateRoots(function() {
         if (changeDirectoryTo) {
           self.directoryModel_.changeDirectory(changeDirectoryTo);
         }
@@ skipping 1606 matching lines @@
 
       handleSplitterDragEnd: function(e) {
         Splitter.prototype.handleSplitterDragEnd.apply(this, arguments);
         this.ownerDocument.documentElement.classList.remove('col-resize');
       }
     };
 
     customSplitter.decorate(splitterElement);
   };
 })();