Sketch splitting SkPicture into an interface and SkBigPicture.

Adds small pictures for drawRect(), drawTextBlob(), and drawPath().
These cover about 89% of draw calls from Blink SKPs,
and about 25% of draw calls from our GMs.

SkPicture handles:
  - serialization and deserialization
  - unique IDs

Everything else is left to the subclasses:
  - playback(), cullRect()
  - hasBitmap(), hasText(), suitableForGPU(), etc.
  - LayerInfo / AccelData if applicable.

The time to record a 1-op picture improves a good chunk
(2 mallocs to 1), and the time to record a 0-op picture
greatly improves (2 mallocs to none):

    picture_overhead_draw:   450ns -> 350ns
    picture_overhead_nodraw: 300ns -> 90ns

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/c92c129ff85b05a714bd1bf921c02d5e14651f8b

Latest blink_linux_rel:

http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/61248

Committed: https://skia.googlesource.com/skia/+/15877b6eae33a9282458bdb904a6d00440eca0ec

http://build.chromium.org/p/tryserver.blink/builders/linux_blink_rel/builds/62015

Review URL: https://codereview.chromium.org/1112523006
26 files changed