Apply WTF::ParamStorageTraits<> to CrossThreadTaskN.

Apply WTF::ParamStorageTraits<> to CrossThreadTaskN.

Before this CL, a pointer to a GarbageCollected object is stored by RawPtr<T> or
T* in CrossThreadTaskN.  If a GC happened before the task is performed,
the object can be swept.

Applying ParamStorageTraits makes it CrossThreadPersistent<T>, and
we can safely use createCrossThreadTask() for GarbageCollected objects.

BUG=378192
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=190638

[tkent, 2015-02-18 07:09:26]

Patchset #1 (id:1) has been deleted

[tkent, 2015-02-18 07:33:42]

Patchset #1 (id:20001) has been deleted

[tkent, 2015-02-18 09:22:11]

tkent@chromium.org changed reviewers:
+ hiroshige@chromium.org, oilpan-reviews@chromium.org

[tkent, 2015-02-18 09:22:11]

Please review this.

[kouhei (in TOK), 2015-02-18 12:29:59]

kouhei@chromium.org changed reviewers:
+ kouhei@chromium.org

[kouhei (in TOK), 2015-02-18 12:29:59]

lgtm

[hiroshige, 2015-02-19 06:44:35]

lgtm in terms of thread safety. (but not sure about Oilpan-related issues)

[tkent, 2015-02-23 06:11:18]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2015-02-23 06:11:43]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/934963003/40001

[commit-bot: I haz the power, 2015-02-23 06:14:50]

Committed patchset #1 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=190638