Add two new gfx::Tween::Types and use one of them for the timing function for the overview mode animation

BUG=334428
TEST=None

Review URL: https://codereview.chromium.org/143413020

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@248967 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 248967