Make CursorFactoryOzone methods virtual

These need to be overridden by platforms and must be virtual.

BUG=252315
TBR=rjkroege
NOTRY=true

Review URL: https://codereview.chromium.org/189413002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255466 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255466
Rebaseline Pixel.CSS3DBlueBox for Blink r168634.

The test's only failing on the Android GPU bot, but this will
necessarily regenerate the reference images on all of the bots.

BUG=350043
R=zmo@chromium.org

Review URL: https://codereview.chromium.org/189533003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255467 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255467