fix #7194

Auditors: @bsclifton, @bbondy

Test Plan:

a. getNextFolderName covered by unittest

b. Import bookmark:
1. Import bookmarks from other browser or html
2. There will always a folder contains the imported bookmarks
3. If the folder name already exist,
  it will be "Imported from XXX (1)", "Imported from XXX (2)" ... etc