At startup, we allocate a few scratch arrays and then use those
instead of having to malloc and free a bunch of arrays during
runtime.
The benchmark that was added is a bit noisy (probably because
of the garbage collection going on from the created Float32Arrays),
but a few percent faster.
We also don't set the paragraph background/foreground colors to
transparent because we check them being falsey before sending them
over the wire. I noticed that if foreground was transparent black,
no text shows up at all, which was unexpected.
Change-Id: I9f3a590a122d7de222cb5f58ea40e86b2d261c96
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/292685
Reviewed-by: Nathaniel Nifong <nifong@google.com>
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