Oilpan: fix failing animation unit tests.

Oilpan: fix failing animation unit tests.

Address three failures:

 * AnimationTest.ElementDestructorClearsAnimationTarget
   Animation objects now die with their target element, hence testing
   for it separately being destructed doesn't make sense in an
   Oilpan setting.
 * AnimationStackTest.ForwardsFillDiscarding
   In order to be able to accurately sample the number of effects on
   the stack, explicitly GC before querying.
 * AnimationPlayerTest.AttachedAnimationPlayers
   Use a persistent to correctly hold on to the test element. If not,
   the final GC will destruct it also & making any further testing
   over it invalid.

R=haraken@chromium.org
BUG=340522
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=174261

[sof, 2014-05-18 14:49:16]

Please take a look.

[haraken, 2014-05-18 19:07:41]

LGTM. I'm sorry I didn't take care of those failures...

[sof, 2014-05-18 19:54:25]

On 2014/05/18 19:07:41, haraken wrote:
> LGTM. I'm sorry I didn't take care of those failures...

Thanks, just details to make builds look a bit greener :)

Well, ImageBitmapTest.ImageBitmapLiveResourcePriority has started (occasionally)
failing recently & is the only unit test failure right now. I've not been able
to reproduce.

[sof, 2014-05-18 19:54:54]

The CQ bit was checked by sigbjornf@opera.com

[commit-bot: I haz the power, 2014-05-18 19:55:11]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/sigbjornf@opera.com/287343003/1

[haraken, 2014-05-18 21:59:49]

On 2014/05/18 19:54:25, sof wrote:
> On 2014/05/18 19:07:41, haraken wrote:
> > LGTM. I'm sorry I didn't take care of those failures...
> 
> Thanks, just details to make builds look a bit greener :)
> 
> Well, ImageBitmapTest.ImageBitmapLiveResourcePriority has started
(occasionally)
> failing recently & is the only unit test failure right now. I've not been able
> to reproduce.

Yeah, I also tried to reproduce the failure in my local Linux/Debug build last
week, I couldn't reproduce it either.

[commit-bot: I haz the power, 2014-05-19 10:09:34]

Change committed as 174261