Remove a FIXME related to SkDevice refactoring

BUG=278148

Review URL: https://codereview.chromium.org/126163002

git-svn-id: svn://svn.chromium.org/blink/trunk@164636 bbb929c8-8fbe-4397-9dbb-9b2b20218538
use default for 2nd parameter in setPixelRef, as that signature is changing, and the size_t version is deprecated

BUG=

Review URL: https://codereview.chromium.org/126673002

git-svn-id: svn://svn.chromium.org/blink/trunk@164637 bbb929c8-8fbe-4397-9dbb-9b2b20218538