scale xmin and xmax for FontMetrics

BUG=skia:

Review URL: https://codereview.chromium.org/685153004
Discard atlas after every MultiPictureDraw::draw

This is intended to prevent ghosting on tiled architectures.

This CL also defers creation of the atlas (and its texture) until it is actually needed.

Committed: https://skia.googlesource.com/skia/+/6d5b5455743414ddb11d2b8c1fe9d7959f2b853d

Review URL: https://codereview.chromium.org/678403002
Moving weather pageset since it is crashing
Try out SkTree in nanobench.

Looks like a fairly large recording speed win with no playback cost.

BUG=skia:

Review URL: https://codereview.chromium.org/653023003
SkTaskGroup::batch(fn, args, N)

Porting QuiltTask isn't important in itself; this is mostly an API feeler.

BUG=skia:

Review URL: https://codereview.chromium.org/689673003
Increase timeouts of wowwiki and youtube