So we'll no longer write into the legacy datastore.

Refactor FlRenderer to platform-independent implementation

https://skia.googlesource.com/skia.git/+log/931cad1d74bb..e9e8e5d771c5

2021-02-02 kjlubick@google.com [canvaskit] Replace Postan value array with Float32Array.
2021-02-02 kjlubick@google.com [canvaskit] Remove deprecated PathMeasure
2021-02-02 kjlubick@google.com [canvaskit] Remove value_array for vector3
2021-02-02 kjlubick@google.com [canvaskit] Replace Point value_array with Float32Array
2021-02-02 mtklein@google.com silo away td when -local
2021-02-02 mtklein@google.com add ASAN FM bot
2021-02-02 johnstiles@google.com Avoid comma usage in Operators test.
2021-02-02 adlai@google.com Handle fDeferredProxies in GrOpsTask merging

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 robertphillips@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