Reland https://codereview.chromium.org/929043002/: Add a presubmit check that warns about declaring…

Reland https://codereview.chromium.org/929043002/: Add a presubmit check that warns about declaring Singleton<T> in header files

Add a presubmit check that warns about declaring Singleton<T> in header files
(except for base/memory/singleton.h)
This check is copied from presubmit_canned_checks.py in depot_tools/ with an
added exception for base/memory/singleton.h.
The corresponding code will be removed from presubmit_canned_checks.py afterwards.

BUG=349861
Committed: https://crrev.com/e61efad3b33f83c9bc990cadaae63ba347173ac4
Cr-Commit-Position: refs/heads/master@{#316852}

[Alexander Potapenko, 2015-02-18 11:16:15]

glider@chromium.org changed reviewers:
+ phajdan.jr@chromium.org

[Alexander Potapenko, 2015-02-18 11:16:15]

PTAL
I've modified MockInputApi.ReadFile() to accept both string file paths and
MockAffectedFile objects, like input_api.ReadFile() does.

Sorry for picking you too often these days :)

[Paweł Hajdan Jr., 2015-02-18 13:11:51]

LGTM

[Alexander Potapenko, 2015-02-18 16:45:23]

The CQ bit was checked by glider@chromium.org

[commit-bot: I haz the power, 2015-02-18 16:45:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/933253002/20001

[commit-bot: I haz the power, 2015-02-18 17:39:51]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-02-18 17:41:26]

Patchset 2 (id:??) landed as
https://crrev.com/e61efad3b33f83c9bc990cadaae63ba347173ac4
Cr-Commit-Position: refs/heads/master@{#316852}