simplify code in SkRecords.h

   - use C++11 features ({} init, move constructors) to eliminate the need
     for explicit constructors
   - collapse RECORD0...RECORD8 into just one RECORD macro
   - explicitly tag record types instead of using member detectors.

Removing member detectors makes this code significantly less fragile.

This exposes a few places where we didn't really think through what to do
with SkDrawable.  I've marked them TODO for now.

BUG=skia:

Review URL: https://codereview.chromium.org/1360943003
10 files changed