* [fuchsia] fix Rasterizer::ScreenshotLayerTreeAsPicture on Fuchsia

* [fuchsia] Add shell test for skp based shader warmup

* [fuchsia] use custom image serialization when writing out SKP's

This change adds custom image serialization functions for skp serialization
which write out onlythe image metadata and not the contents of the
images themselves. This allows SKP's to be used for shader warmup with
a significantly reduced disk space footprint.

https://skia.googlesource.com/skia.git/+log/c97ebe06dc1d..f2d90659ff1a

2020-07-17 fmalita@chromium.org [skottie] Fix analytical mask fill type
2020-07-17 johnstiles@google.com Add an input FP to the GrProcessorTestData.
2020-07-17 robertphillips@google.com Clean up some GrContext uses in the GMs
2020-07-17 adlai@google.com Remove two unused deprecated SkImage functions
2020-07-17 nifong@google.com fix heap-buffer-overflow by not returning string from reportBackendType
2020-07-17 brianosman@google.com fuzz: Add 'loops' option to run multiple times
2020-07-17 westont@google.com Add updated provisioning_profile_ios that includes iphone 11s.
2020-07-17 herb@google.com create SkAtlasSubRun API subclass SkMaskSubRun
2020-07-17 herb@google.com make prepareGrGlyphs private
2020-07-17 herb@google.com remove unused calls: grGlyph and quadOffset

If this roll has caused a breakage, revert this CL and stop the roller
using the controls here:
https://autoroll.skia.org/r/skia-flutter-autoroll
Please CC nifong@google.com on the revert to ensure that a human
is aware of the problem.

To report a problem with the AutoRoller itself, please file a bug:
https://bugs.chromium.org/p/skia/issues/entry?template=Autoroller+Bug

Documentation for the AutoRoller is here:
https://skia.googlesource.com/buildbot/+doc/master/autoroll/README.md

* Add CPU-only rendering mode for CanvasKit as a fallback

This implements the design in flutter.dev/go/handling-synchronous-keyboard-events for Android.

I started with Android, but this will be used for all platforms as we add them.

The related framework PR is: flutter/flutter#59358 (which has already landed)