Revert 91861 - When the download folder does not exist, change the download folder to a user's "D...

Revert 91861 - When the download folder does not exist, change the download folder to a user's "Downloads" (or something depending on the platform)

Description of reverted commit follows:
  - Set the download folder to Foo. You can download a PDF file to Foo without being asked anything (if you do not choose "Ask where to save each file before downloading"). Then delete Foo. Now, if you try to download the PDF file, then a file chooser dialog is displayed suggesting your "Downloads" folder.
  - Set the download folder to Foo. Save an HTML to Bar by right-clicking and choosing "Save as ..." on the tab. If you try to save the HTML, the file chooser dialog is displayed suggesting Bar. Then delete Bar. Now, if you try to save the HTML, the file chooser dialog is displayed suggesting Foo. Then delete Foo. If you try to save the HTML, the file chooser dialog is displayed suggesting your "Downloads" folder.
  - Set the download folder to Foo. Observe that Foo is displayed as the download location in the preferences page. Then delete Foo and reload the preferences page. Observe that your "Downloads" folder is displayed as the download location in the preferences page. If you are opening multiple preferences pages, then this change is automatically reflected to all the preferences pages.
  BUG=32552
TEST=SavePageBrowserTest.SavedFolder1,SavePageBrowserTest.SavedFolder2,SavePageBrowserTest.SavedFolder3,DownloadTest.DownloadedFolder,DownloadManagerTest.StartDownload,BaseFileTest.*,DownloadFileTest.RenameFileFinal
  Review URL: http://codereview.chromium.org/6973052

TBR=haraken@google.com
Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=91869