allocator changes

[Will]

Hi,

I will soon be landing some changes to the allocator in Chromium.  This shouldn't have any knock-on effects on other platforms than Windows, but since the deep memory profiler is very much interlinked with how tcmalloc and the allocator works, I wanted to give this group a heads up.  Feel free to comment on the CL:

https://codereview.chromium.org/774683003/

I will be testing everything with the dmp instructions on http://www.chromium.org/developers/deep-memory-profiler before landing!

Cheers,

Will