Reland 1: "mac: Add auto-close and share-read-only functionality to SharedMemory."

Reland 1: "mac: Add auto-close and share-read-only functionality to SharedMemory."

The original CL had a bug in the unit tests where an incorrect
parameter was passed to mach_vm_region.

> base::FileDescriptor has a property |auto_close| that is used to indicate that
> when the object is passed to an IPC message, the message takes ownership of the
> underlying OS handle. Since SharedMemoryHandle needs to be interchangeable with
> base::FileDescriptor, I added a property with similar functionality named
> |ownership_passes_to_ipc_|.
>
> The method ShareToProcess() is used to lower the current and maximum protection
> of the underlying OS handle before it is transferred to a different process. I
> implemented this functionality for Mach memory objects.
>
> BUG=535711
> Committed: https://crrev.com/033bbbcb63cab781552dfb435c035131c423de30
> Cr-Commit-Position: refs/heads/master@{#355880}

BUG=535711
TBR=tsepez@chromium.org, mark@chromium.org

Committed: https://crrev.com/328bf3f3a685d97426e9095b7b3d58836ef665b0
Cr-Commit-Position: refs/heads/master@{#355941}

[erikchen, 2015-10-23 23:02:33]

erikchen@chromium.org changed reviewers:
+ mark@chromium.org, tsepez@chromium.org

[erikchen, 2015-10-23 23:02:34]

tbr-ing tsepez@ and mark@ since the error was trivial:

In a unit test, I was passing an uninitialized parameter to mach_vm_region. When
the parameter is <= VM_REGION_BASIC_INFO_COUNT_64, the test would fail, which
explains the single error on the waterfall.

[erikchen, 2015-10-23 23:03:19]

The CQ bit was checked by erikchen@chromium.org

[commit-bot: I haz the power, 2015-10-23 23:04:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1422873002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1422873002/20001

[Mark Mentovai, 2015-10-23 23:09:11]

LGTM

[commit-bot: I haz the power, 2015-10-24 00:47:02]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-10-24 00:49:33]

Patchset 2 (id:??) landed as
https://crrev.com/328bf3f3a685d97426e9095b7b3d58836ef665b0
Cr-Commit-Position: refs/heads/master@{#355941}