Mark GetCallingContext as soon-to-be deprecated

Mark GetCallingContext as soon-to-be deprecated

The calling context is the second top-most non-debugger context on the
stack, but that's not necessarily the actually calling context, e.g.,
when a tail-call was used.

BUG=chromium:541703
R=verwaest@chromium.org
LOG=y

Committed: https://crrev.com/16ca5c61025dd414b33afa88db0b8c287bac2f26
Cr-Commit-Position: refs/heads/master@{#31719}

[jochen (gone - plz use gerrit), 2015-10-30 13:41:38]

The CQ bit was checked by jochen@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-10-30 13:42:21]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431473003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431473003/1

[commit-bot: I haz the power, 2015-10-30 14:53:51]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-10-30 14:53:51]

Dry run: This issue passed the CQ dry run.

[Toon Verwaest, 2015-11-02 09:24:55]

lgtm

[jochen (gone - plz use gerrit), 2015-11-02 19:02:17]

The CQ bit was checked by jochen@chromium.org

[commit-bot: I haz the power, 2015-11-02 19:02:28]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431473003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431473003/1

[commit-bot: I haz the power, 2015-11-02 19:22:40]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-02 19:23:19]

Patchset 1 (id:??) landed as
https://crrev.com/16ca5c61025dd414b33afa88db0b8c287bac2f26
Cr-Commit-Position: refs/heads/master@{#31719}