GitLab

Separate all interactions with HistoryService out of DownloadManager
to new class DownloadHistory owned by the DownloadManager.

The goal is to create more smaller classes with clearly defined
responsibilities.

TEST=unit_tests, browser_tests, ui_tests
BUG=48913

Review URL: http://codereview.chromium.org/3071005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@54205 0039d316-1c4b-4281-b951-d872f2087c98