Initialized ImageData with transparent black when constructed with no data

This behavior is already tested, and the test already passes (by coincidence?)
even though we were using creteUninitialize to allocate the data array.

BUG=361694

Review URL: https://codereview.chromium.org/230823005

git-svn-id: svn://svn.chromium.org/blink/trunk@171170 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Reenable device-emulation-scale-only test on Mac.

BUG=356743
TBR=pfeldman@chromium.org

Review URL: https://codereview.chromium.org/230623002

git-svn-id: svn://svn.chromium.org/blink/trunk@171171 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Make optional the transform argument of Path2D.addPath

BUG=361686

Review URL: https://codereview.chromium.org/231453002

git-svn-id: svn://svn.chromium.org/blink/trunk@171172 bbb929c8-8fbe-4397-9dbb-9b2b20218538
[CSS Shapes] large corner radius combined with 0 radius does not wrap properly

Corrected special case handling for shape-outside border-box values with border-radius
values that greater than or equal to the box's height.

This is a merge of http://trac.webkit.org/changeset/166966 by Hans Muller <hmuller@adobe.com>.

BUG=361329

Review URL: https://codereview.chromium.org/230403003

git-svn-id: svn://svn.chromium.org/blink/trunk@171173 bbb929c8-8fbe-4397-9dbb-9b2b20218538