Reland "Better first-class shader & color filter support in runtime effects"

This is a reland of adadb95a9f1ef21ccc5264c7d0bdc83b56cf91e9
... adds a temporary workaround for some Android framework code.

Original change's description:
> Better first-class shader & color filter support in runtime effects
>
> This does a few things, because they're all intertwined:
>
> 1) SkRuntimeEffect's API now includes details about children (which Skia
>    stage was declared, not just the name). The factories verify that the
>    declared types in the SkSL match up with the C++ types being passed.
>    Today, we still only support adding children of the same type, so the
>    checks are simple. Once we allow mixing types, we'll be testing the
>    declared type against the actual C++ type supplied for each slot.
> 2) Adds sample variants that supply the input color to the child. This
>    is now the only way to invoke a colorFilter child. Internally, we
>    support passing a color when invoking a child shader, but I'm not
>    exposing that. It's not clearly part of the semantics of the Skia
>    pipeline, and is almost never useful. It also exposes users to
>    several inconsistencies (skbug.com/11942).
> 3) Because of #2, it's possible that we can't compute a reusable program
>    to filter individual colors. In that case, we don't set the constant
>    output for constant input optimization, and filterColor4f falls back
>    to the slower base-class implementation.
>
> Bug: skia:11813 skia:11942
> Change-Id: I06c41e1b35056e486f3163a72acf6b9535d7fed4
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/401917
> Commit-Queue: Brian Osman <brianosman@google.com>
> Reviewed-by: Mike Klein <mtklein@google.com>

Bug: skia:11813 skia:11942
Change-Id: I2c31b147ed86fa8c4dddefb7066bc1d07fe0d285
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/404637
Reviewed-by: Brian Salomon <bsalomon@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
19 files changed