Merge 181957

Merge 181957
> [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

TBR=shawnsingh@chromium.org
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182808