SkRecord: clean up comments and 4 bytes per SkRecord.

Just happened to notice these while skimming through.  The comments are a
little out of date; now that we have visit/mutate, we do need O(1) random
access.

The constructor arguments are flexibility we're not using.

BUG=skia:
R=fmalita@google.com

Author: mtklein@skia.org

Review URL: https://codereview.chromium.org/569373002
1 file changed