Fix crasher with autofill infobar.
The "save credit card" information was deleted by the AutofillManager when the form is submitted but was still pointed to by the TabContents, causing a crasher when navigating.

BUG=50428
TEST=See steps in 56238.

Review URL: http://codereview.chromium.org/3466006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@60095 0039d316-1c4b-4281-b951-d872f2087c98
AutoFillManager::AutoFillManager(TabContents* tab_contents,
                                 PersonalDataManager* personal_data)
    : tab_contents_(tab_contents),
      personal_data_(personal_data),
      download_manager_(NULL),
      disable_download_manager_requests_(false) {
  DCHECK(tab_contents);
}

AutoFillManager::AutoFillManager(TabContents* tab_contents,
                                 PersonalDataManager* personal_data)
    : tab_contents_(tab_contents),
      personal_data_(personal_data),
      download_manager_(NULL),
      disable_download_manager_requests_(false) {
  DCHECK(tab_contents);
}
