Make passing of DownloadRequestHandle separate from DownloadCreateInfo.

This is to support mocking DownloadRequestHandle.

BUG=101214

Review URL: http://codereview.chromium.org/8371009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@107219 0039d316-1c4b-4281-b951-d872f2087c98
13 files changed