Tune rosalloc buffer sizes.

We now use one-page buffers for size brackets 4-7, instead of two-page
buffers, and the first 8 size brackets for thread-local allocations,
instead of 11.

No slowdown observed with MemAllocTest, EvaluateAndApplyChanges, and
BinaryTrees.

Bug: 18377775

Change-Id: Ie1bb46bcf5d3729197e48e26a27da4cc39dd807e
2 files changed