Remove SkCanvas::LayerIter used in SkCanvasStateUtils

The LayerIter existed to iterate over the top-most device and any
unclipped layers connected to it. With unclipped layers gone,
SkCanvasStateUtils can just access the top-most device using other
APIs.

Bug: skia:10986
Change-Id: I260ec37fcc8e39d1ec2972a3297521d714649cb5
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/339991
Commit-Queue: Michael Ludwig <michaelludwig@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Reviewed-by: Derek Sollenberger <djsollen@google.com>
3 files changed