Implement new overlay scrollbar specs

Make overlay scrollbars thicken only on mouse movement (not scrolling).
Keep the bars thick as long as the mouse is near them.
Thicken and darken the bars through an animation.
Make the distance to thicken the bars 25 dips (instead of 100).

BUG=299046,274010
R=enne@chromium.org, enne, tony

Review URL: https://codereview.chromium.org/40603006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231118 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231118
Get rid of the two test RenderViewHostObservers in chrome. This also removes two RenderViewHost::AddCreatedCallback calls which are deprecated as well.

BUG=306569
R=avi@chromium.org, scr@chromium.org

Review URL: https://codereview.chromium.org/43543002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231119 0039d316-1c4b-4281-b951-d872f2087c98
Add a new histogram to track the number of total of QUIC streams created when a QUIC session crypto handshake timed out.

Net.QuicSession.ConnectionClose.NumTotalStreams.HandshakeTimedOut

Review URL: https://codereview.chromium.org/44613002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@231120 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 231119
SVN changes up to revision 231120