Remove legacy size classes. - #972
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want_legacy_size_classes has been a no-op for a while without any complaints, so now remove the underlying code. We still keep the target, but will clean it up in a future step. Note that this is not a no-op for generated code; the maximum number of size classes drops, which means several structures (e.g., the per-CPU metadata slabs) become smaller, _and_ that we can fit CompactSizeClass (used in the page map) into one byte instead of two. This means PageMap3::Leaf shrinks from 10*kLeafLength bytes to 9*kLeafLength, a 10% decrease. PiperOrigin-RevId: 983725554
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Remove legacy size classes.
want_legacy_size_classes has been a no-op for a while without any
complaints, so now remove the underlying code. We still keep
the target, but will clean it up in a future step.
Note that this is not a no-op for generated code; the maximum number
of size classes drops, which means several structures (e.g.,
the per-CPU metadata slabs) become smaller, and that we can fit
CompactSizeClass (used in the page map) into one byte instead of two.
This means PageMap3::Leaf shrinks from 10kLeafLength bytes to
9kLeafLength, a 10% decrease.