Remove unused and undefined RenderImage::highQualityRepaintTimerFired

Not be confused with the one in ImageQualityController.

BUG=

Review URL: https://codereview.chromium.org/609293003

git-svn-id: svn://svn.chromium.org/blink/trunk@182854 bbb929c8-8fbe-4397-9dbb-9b2b20218538