Fix debugger's SaveAs functionality

Without this patch the SaveAs functionality only copies the portion of the picture from the current command in the GUI.

Review URL: https://codereview.chromium.org/672453002
use - and = to zoom text in slides

BUG=skia:
TBR=
NOTRY=True

Review URL: https://codereview.chromium.org/668023002
small tweaks to SkResourceCache::Key
  - remove unused method and obsolete note
  - add a reminder that yes, we are checking counts are equal

BUG=skia:

Review URL: https://codereview.chromium.org/667993002
Widen the set of nested rects that can be drawn natively on the GPU

GrAARectRenderer::fillAANestedRects only handles thin stroked rects correctly if the margins are all the same. It is also correct if all the margins are >= 1.0f. This CL allows such cases to use the fillAANestedRects fast path.

This seems to halve the gpu rendering time of the picture in bug crbug.com/425427.

Review URL: https://codereview.chromium.org/672473002