rotateRadians function was added to AffineTransform class.
We can switch from some rotate() to rotateRadians().

https://codereview.chromium.org/166273019/

Review URL: https://codereview.chromium.org/173593002

git-svn-id: svn://svn.chromium.org/blink/trunk@168929 bbb929c8-8fbe-4397-9dbb-9b2b20218538