Get rid of fastMallocGoodSize() and replace it with something generic.

- fastMallocGoodSize() was Mac-specific and it looks relatively slow and
non-inlineable. The replacement is based around a single lookup into a small
table.
- We now have allocation quantization on all platforms for Vector. I've
verified that many Vector instantiations are able to recover previously-wasted
memory as real element capacity. See bug for details.
- The quantization is also immediately suitable for use with the Partition
allocator, to avoid fragmentation due to excessive numbers of buckets. To be
followed up in a future patch series.


BUG=286477

Review URL: https://chromiumcodereview.appspot.com/23604048

git-svn-id: svn://svn.chromium.org/blink/trunk@157524 bbb929c8-8fbe-4397-9dbb-9b2b20218538