Clean up a bit after SkPictureData/SkPicturePlayback split

Clean up a bit after SkPictureData/SkPicturePlayback split

This CL begins setting up the SkPicturePlayback split by simplifying the class and componentizing it a bit. It:
  fuses SkPictureData::OperationList into SkPicture::OperationList
  adds a handleOp method to SkPicturePlayback that can be reused by derived classes
  removes a couple debugging tools (ENABLE_TIME_DRAW & SPEW_CLIP_SKIPPING)

R=mtklein@google.com, reed@google.com

Author: robertphillips@google.com

Review URL: https://codereview.chromium.org/378703002