Adding PrintTo of ObjectPath for gtest.

Adding PrintTo of ObjectPath.

PrintTo is used by gtest/gmock for pretty printing.
This change makes debugging tests easier.

BUG=NONE

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=193920

[pneubeck (no reviews), 2013-04-11 08:03:38]

Splitted into separate CL as suggested.
I also removed the string constants "ObjectPath(" and ")", so that the overhead
in binary size is minimized.

I will also start a discussion about this topic on chromium-dev.

[satorux1, 2013-04-11 08:18:20]

Thank you for splitting. I'll be happy to l-g-t-m if the discussion on
chromium-dev is positive about adding PrintTo().

[satorux1, 2013-04-12 06:02:19]

LGTM. No one seems to feel strongly about it. :)

[commit-bot: I haz the power, 2013-04-12 06:37:54]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pneubeck@chromium.org/13942004/1

[commit-bot: I haz the power, 2013-04-12 09:20:51]

Retried try job too often on win_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=win_rel&nu...

[commit-bot: I haz the power, 2013-04-12 09:27:09]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/pneubeck@chromium.org/13942004/1

[commit-bot: I haz the power, 2013-04-12 14:16:37]

Change committed as 193920