PartitionAlloc: Distinguish OOMs where a lot of super pages are not committed.

This CL distinguishes
specific OOMs (where a lot of super pages are allocated but not committed) from
actual OOMs (where a lot of physical memory is allocated) in crash reports.
- By crashing in partitionOutOfMemoryWithLotsOfUncommitedPages.
- By crashing at a special address (0x9b) in Windows, because reported stack
  traces are not accurate.
This check is enabled on 32-bit environments only.

BUG=421387

Review URL: https://codereview.chromium.org/683043002

git-svn-id: svn://svn.chromium.org/blink/trunk@185286 bbb929c8-8fbe-4397-9dbb-9b2b20218538