Rename ChunkBits to kChunkBits.
Rename ChunkBits to kChunkBits.

go/skiastyle: "Variables declared constexpr or const, and whose value is
fixed for the duration of the program, are named with a leading "k" and
then camel-capped."

Change-Id: Id9cf292a923d6b4db760975ffb7bc1a04c516e87
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/322440
Commit-Queue: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Reviewed-by: Brian Osman <794c0b5534edf5601d88e1d41975d0262da12894@google.com>
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>

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