Add an UMA for file types selected when Quick View is launched.

BUG=627697
TEST=opened a file and moved to the next with <Right> and checked chrome://histograms. Confirmed 1 FileBrowser.QuickView.FileTypeOnLaunch is exported and 2 FileBrowser.QuickView.FileType are exported.

Review-Url: https://codereview.chromium.org/2252723005
Cr-Commit-Position: refs/heads/master@{#412761}
2 files changed