Revert "base: Introduce the new Shared Memory API"

This reverts commit cdd8661f3f35d7075020ead0492cd83e18f795e9.

Reason for revert:

Findit (https://goo.gl/kROfz5) identified CL at revision 545521 as the
culprit for failures in the build cycles as shown on:
https://findit-for-me.appspot.com/waterfall/culprit?key=ag9zfmZpbmRpdC1mb3ItbWVyRAsSDVdmU3VzcGVjdGVkQ0wiMWNocm9taXVtL2NkZDg2NjFmM2YzNWQ3MDc1MDIwZWFkMDQ5MmNkODNlMThmNzk1ZTkM

Sample Failed Build: https://ci.chromium.org/buildbot/chromium.linux/Linux%20Tests%20%28dbg%29%281%29%2832%29/48976

Sample Failed Step: base_unittests

Original change's description:
> base: Introduce the new Shared Memory API
> 
> Design doc (public): https://goo.gl/HmBYy6
> 
> This patch proposes the new API for the Shared Memory based on two
> concepts, a shared memory region and a shared memory mapping. The
> region controls the platform-specific handle and mediates sharing and
> access control. The mapping is just a reference to the memory bytes
> which knows how to unmap itself. Ownership is per-instance: neither a
> region nor a mapping may be copied, and resources are freed when then
> instance dies. This is accomplished through move-only semantics.
> 
> The goal of the new API is to provide a correct cross-platform
> implementation that makes the sharing mode explicit via the C++ type
> system.
> 
> Thus, this CL introduces two classes for shared memory mappings:
> - WritableSharedMemoryMapping owns and provides an access to writable
> shared memory
> - ReadOnlySharedMemoryMapping for read-only shared memory
> 
> and three classes representing shared memory regions:
> - UnsafeSharedMemoryRegion allows to create
> WritableSharedMemoryMapping instances and cannot be used for making
> read-only mappings
> - ReadOnlySharedMemoryRegion, on the contrary, can produce only
> ReadOnlySharedMemoryMapping instances and it also creates one writable
> mapping in the caller process address space
> - WritableSharedMemoryRegion allows to create writable
> mappings and can be eventually converted to ReadOnlySharedMemoryRegion.
> The important limitation in comparison with UnsafeSharedMemoryRegion
> is that the WritableSharedMemoryRegion cannot be duplicated so in
> order to pass the writable region to another process, the ownership of
> the region must be moved/transferred to this process.
> 
> Bug: 795291
> Change-Id: I7d1d0a24932145cc0f449b01ceb8cafef9b7e407
> Reviewed-on: https://chromium-review.googlesource.com/893458
> Commit-Queue: Alexandr Ilin <alexilin@chromium.org>
> Reviewed-by: Matthew Cary <mattcary@chromium.org>
> Reviewed-by: Daniel Cheng <dcheng@chromium.org>
> Reviewed-by: Erik Chen <erikchen@chromium.org>
> Reviewed-by: Robert Sesek <rsesek@chromium.org>
> Reviewed-by: Ken Rockot <rockot@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#545521}

Change-Id: I9c5657e80b8a262a42311d4d2a0239dc242ab8f5
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: 795291
Reviewed-on: https://chromium-review.googlesource.com/978563
Cr-Commit-Position: refs/heads/master@{#545568}
25 files changed