SkDraw.h #include cleanup

Removal of SkAutoKern header was already done in r8495; this just
lands the replacement of #includes with forward declarations for
incremental compile speed.

https://codereview.appspot.com/8109043/



git-svn-id: http://skia.googlecode.com/svn/trunk@8504 2bbb7eff-a529-9590-31e7-b0007b416f81
1 file changed