This reverts commit ee5c31f3.

Reason for revert: Fixed compiler failure

Original change's description:
> Revert "[wasm] A simple allocator datastructure for off-the heap"
> 
> This reverts commit 110d9ab0.
> 
> Reason for revert: https://build.chromium.org/p/client.v8/builders/V8%20Linux64%20-%20debug%20builder/builds/26607
> 
> Surprising we're seeing a failure on Linux 64 *after* CQ. Is the compiler there different?
> 
> Original change's description:
> > [wasm] A simple allocator datastructure for off-the heap
> > 
> > We'll use this allocator in a follow-up CL to:
> > - allocate speculative sizes of memory for a module that's being
> > compiled (e.g. 2*size of wasm code).
> > - each module will own such a sub-pool, and then use it to allocate
> > contiguous chunks of memory for code.
> > 
> > The underlying assumptions for the chosen allocation strategy is that:
> > - the allocation granularity for pools is 1 page, so that no one page
> > is owned by more than one wasm module
> > - typical pool sizes (given module sizes) are multiple pages.
> > - modules and module instances are typically few and long lived. Typically,
> > we expect one module and one instance. 
> > 
> > This means we shouldn't expect fragmentations that lead to code being
> > non-allocatable, or prohibitively many ranges.
> > 
> > The data structure just manages ranges of addresses. Virtual memory management
> > will be separate, as part of the responsibility of a "WasmHeap"
> > that will be introduced in the future. So will concurrency control.
> > 
> > Bug: 
> > Change-Id: Id99f46d10c25553b013054d994760f3c2a737c39
> > Reviewed-on: https://chromium-review.googlesource.com/669296
> > Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
> > Reviewed-by: Eric Holk <eholk@chromium.org>
> > Reviewed-by: Brad Nelson <bradnelson@chromium.org>
> > Cr-Commit-Position: refs/heads/master@{#48053}
> 
> TBR=bradnelson@chromium.org,mtrofin@chromium.org,eholk@chromium.org
> 
> Change-Id: Id82fa341b77624e4971f24c4757a9a666a65930c
> No-Presubmit: true
> No-Tree-Checks: true
> No-Try: true
> Reviewed-on: https://chromium-review.googlesource.com/670141
> Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
> Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#48054}

TBR=bradnelson@chromium.org,mtrofin@chromium.org,eholk@chromium.org

Change-Id: Ib6a7a3e6098d2689e60cdca85ec77e57e5295e48
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/670142
Commit-Queue: Mircea Trofin <mtrofin@chromium.org>
Reviewed-by: Mircea Trofin <mtrofin@chromium.org>
Cr-Commit-Position: refs/heads/master@{#48055}