Files.app: Prevent the maximize and the close buttons from stealng focus.

This is achieved by calling prevnet default for mouse down events.

BUG=298844
TEST=manually

Review URL: https://codereview.chromium.org/24995002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225911 0039d316-1c4b-4281-b951-d872f2087c98
Fix uninitialized var in QuicEndToEndTest

TBR=rtenneti@chromium.org

Review URL: https://codereview.chromium.org/25199002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@225912 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 225912