Web Animations CSS: Fall back to legacy behavior of avoiding cross-fades of generated images.

When interpolating between mismatched gradients (and other generated image types), the correct behavior is to cross-fade. However, cross-fading of generated images is not currently implemented in Blink.

This patch reverts to the legacy CSS animation behavior of switching instantaneously between generated images on animation. We should revert this patch when cross-fading of generated images is supported.

BUG=327124

Review URL: https://codereview.chromium.org/111343002

git-svn-id: svn://svn.chromium.org/blink/trunk@163505 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove unnecessary casts to MutationRecord*.

ChildListRecord, AttributesRecord, characterDataRecord, and
MutationRecordWithNullOldValue are subclasses of MutationRecord. We don't need
to cast them to the parent class.

BUG=

Review URL: https://codereview.chromium.org/111103004

git-svn-id: svn://svn.chromium.org/blink/trunk@163506 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Don't check lfQuality in LOGFONT as it has no effect on rendering

Remove the LOGFONT lfQuality check in computePaintTextFlags and instead
base the textFlags entierly on the system ClearType settings (and
whether a font is a web font). Skia will then use this information to
pick the appropriate type of font smoothing to apply (if any).

BUG=249099
R=bungeman@chromium.org

Review URL: https://codereview.chromium.org/99333013

git-svn-id: svn://svn.chromium.org/blink/trunk@163507 bbb929c8-8fbe-4397-9dbb-9b2b20218538