Revert 163198 "Make PageAllocator generic and enhance it to supp..."

> Make PageAllocator generic and enhance it to support arbitrary alignments.
> 
> PageAllocator no longer refers to "super pages", that is a concept specific to
> PartitionAlloc.
> The PageAllocator API is simplified to handle randomization automatically if
> the client passes a NULL address.
> The code to handle aligned allocations was genercized to work on Windows and
> also support arbitrary alignments (this will be needed in the next CL in the
> series). The new code also uses a simpler and easy to understand strategy.
> Finally, make the MappingCollision test run on all platforms.
> 
> There should be no functional changes because the super page size remains 64KB.
> 
> BUG=324960
> 
> Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=163125
> 
> R=tsepez@chromium.org
> 
> Review URL: https://codereview.chromium.org/98443004

TBR=cevans@chromium.org

Review URL: https://codereview.chromium.org/105883005

git-svn-id: svn://svn.chromium.org/blink/trunk@163203 bbb929c8-8fbe-4397-9dbb-9b2b20218538