Revert "memlog: Add task contexts from allocation context to native mode"

This reverts commit 3e6c0cd82b031b55e535968fe527c4df3f4fba5a.

Reason for revert: Causes crashes on Mac while accessing TLS.

Original change's description:
> memlog: Add task contexts from allocation context to native mode
> 
> The task context is useful to debug mojo memory leaks since IPC messages
> are tagged with contexts
> 
> BUG=874530
> 
> Change-Id: Id59d016f963f41fdeda6af69b3c470f0101dbfe7
> Reviewed-on: https://chromium-review.googlesource.com/1232683
> Reviewed-by: Erik Chen <[email protected]>
> Commit-Queue: Siddhartha S <[email protected]>
> Cr-Commit-Position: refs/heads/master@{#593458}

[email protected],[email protected]

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 874530, 888899
Change-Id: I70e2dc4a91f8512dc98a68d5dd0736f5e511da54
Reviewed-on: https://chromium-review.googlesource.com/1244829
Reviewed-by: Siddhartha S <[email protected]>
Commit-Queue: Siddhartha S <[email protected]>
Cr-Commit-Position: refs/heads/master@{#594158}
4 files changed