don't explicitly create SkDevice, as it is intended to be private. Skia now has ways to create a canvas that completely hide the impl-details of SkDevice and its subclasses (mostly).

BUG=skia:1931

Review URL: https://codereview.chromium.org/137833013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253714 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253714