[cc] Apply sublayer transform about anchor instead of about layer center.
There are some cases where WebCore internally needs to "reposition" the origin
point about which CSS transforms are applied. For example, when a perspective
container becomes composited, the composited location/bounds may change
depending on the positioning of its children. The perspective-origin from the
original DOM tree should not change, but internally it does require a new
origin to be given to the compositor. It turns out that WebCore uses the anchor
point layer property to communicate these cases. So, the compositor needs to
apply the sublayer transform about the anchor point instead of about the layer
center.
BUG=157961
Review URL: https://chromiumcodereview.appspot.com/12224113
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@181957 0039d316-1c4b-4281-b951-d872f2087c98
2 files changed
