More SkPicture cleanup
 - move field declarations together and pack them a little tighter
 - get rid of fData
 - remove dead code in debugger, including unused SkPicturePlayback subclass

There are now no more long-lived SkPictureData!  (Really, there never were,
but now we don't pretend to support them.)

BUG=skia:

No API changes.
TBR=reed@google.com

Review URL: https://codereview.chromium.org/725143002
4 files changed