Omnibox Field Trial: Make HQP Score Bookmarks More Highly

Creates a field trial to experiment with giving a bonus to
untyped visits to pages that are bookmarked.  I imagine counting
each visit as 5 visits.  Typed visits can easily swamp visits to
bookmarks.  (Typed visits count 20x.)

Also cleaned up a few comments in the header to refer to
variables with their _ names, not the earlier names (before I
converted ScoredHistoryMatch from a struct to a class).

TBR=sky

BUG=247715

Review URL: https://codereview.chromium.org/67553002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237417 0039d316-1c4b-4281-b951-d872f2087c98
Update webview docs.

BUG=307559
NOTRY=true

Review URL: https://codereview.chromium.org/81423003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237418 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237418
Fix memory leaks in DownloadExtensionTest tests.

Eliminate a circular ref in test code.

BUG=322918
R=benjhayden@chromium.org

Review URL: https://codereview.chromium.org/88883002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237419 0039d316-1c4b-4281-b951-d872f2087c98
Fix the problem that prerender will cause video to not play

BUG=323551

Review URL: https://codereview.chromium.org/89163002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@237420 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 237419
SVN changes up to revision 237420