Make MemoryCoordinator garbage collected

Make MemoryCoordinator garbage collected

To make sure MemoryCoordinator::trace() is called.

[bashi, 2016-08-16 06:20:31]

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

[commit-bot: I haz the power, 2016-08-16 06:20:40]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[bashi, 2016-08-16 06:57:25]

bashi@chromium.org changed reviewers:
+ haraken@chromium.org, keishi@chromium.org, tasak@google.com

[bashi, 2016-08-16 06:57:26]

PTAL?

Sakamoto-san kindly told me that MemoryCoordinator::trace() won't get called
unless it's on heap.

[commit-bot: I haz the power, 2016-08-16 07:47:37]

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

[commit-bot: I haz the power, 2016-08-16 07:47:38]

Dry run: This issue passed the CQ dry run.

[keishi, 2016-08-16 08:41:35]

https://codereview.chromium.org/2251643002/diff/1/third_party/WebKit/Source/p...
File third_party/WebKit/Source/platform/MemoryCoordinator.cpp (right):

https://codereview.chromium.org/2251643002/diff/1/third_party/WebKit/Source/p...
third_party/WebKit/Source/platform/MemoryCoordinator.cpp:23: instance = new
Persistent<MemoryCoordinator>(new MemoryCoordinator);
This may be shorter
DEFINE_STATIC_LOCAL(Persistent<MemoryCoordinator>, external, (new
MemoryCoordinator));

[haraken, 2016-08-16 11:33:47]

LGTM with keishi@'s comment addressed.

[bashi, 2016-08-18 00:13:16]

Description was changed from

==========
Make MemoryCoordinator garbage collected

To make sure MemoryCoordinator::trace() is called.
==========

to

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Make MemoryCoordinator garbage collected

To make sure MemoryCoordinator::trace() is called.
==========