Removed unused code path.

reuse_existing_data is never set true.
It should be removed with https://codereview.chromium.org/26558003

Review URL: https://codereview.chromium.org/81563002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@236642 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 236642