Oilpan: Test/example showing how to get the GC to remove empty sets from a map

Oilpan: Test/example showing how to get the GC to remove empty sets from a map

R=haraken@chromium.org
BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176026

[Erik Corry, 2014-06-12 11:54:39]

In response to a question from Haraken at the meeting Tuesday, the example shows
a weak set as the value type of a map. The GC removes entries from the weak sets
when the objects they reference are collected. When the set is empty, the entry
with that set is removed from the map. This may happen with some delay, so you
can find empty sets in the map and have to guard against that if it's a problem.

[zerny-chromium, 2014-06-12 11:57:13]

lgtm

[Erik Corry, 2014-06-12 12:29:49]

The CQ bit was checked by erik.corry@gmail.com

[commit-bot: I haz the power, 2014-06-12 12:30:21]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/erik.corry@gmail.com/327323008/1

[kouhei (in TOK), 2014-06-12 12:39:34]

lgtm

Thanks for providing an example!

[haraken, 2014-06-12 13:19:37]

LGTM

[commit-bot: I haz the power, 2014-06-12 13:34:40]

Change committed as 176026