Clear m_previousActiveInterpolationsForAnimations in maybeApplyPendingUpdate()

Clear m_previousActiveInterpolationsForAnimations in maybeApplyPendingUpdate()

This is a performance-optimization CL for oilpan builds. In oilpan, it is important
to explicitly clear on-heap collections in order not to leave unnecessary garbage
on the oilpan's heap.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201053

[haraken, 2015-08-24 03:32:25]

haraken@chromium.org changed reviewers:
+ alancutter@chromium.org

[haraken, 2015-08-24 03:32:26]

PTAL

I understand this is a nasty change. I think oilpan should have an ability to
automatically clear an on-heap collection when the collection gets destructed.
However, it is not trivial to make the change without introducing any
performance regression, so I'd like to land this change as a short-term
performance optimization to core/animations with oilpan.

[alancutter (OOO until 2018), 2015-08-24 06:18:43]

lgtm, please add a comment here describing the Oilpan performance gain.

[alancutter (OOO until 2018), 2015-08-24 06:20:43]

Also for the record please reply with any performance numbers you might have
that lead to this change.

[haraken, 2015-08-24 06:45:24]

Patchset #2 (id:20001) has been deleted

[haraken, 2015-08-24 06:53:28]

On 2015/08/24 06:20:43, alancutter wrote:
> Also for the record please reply with any performance numbers you might have
> that lead to this change.

This CL removes 45946 HeapHashMap objects that need to be swept in oilpan's GC
in tough_animation_cases.css_properties_40.html. As a result, this CL should
reduce the number of GCs in oilpan builds.

That said, in practice, this CL doesn't improve performance of
css_properties_40.html because only one GC is scheduled during the benchmark
with the current GC threshold. If the duration of the benchmark is extended or
the GC threshold is lowered (<-- we're planning to do this to reduce the peak
memory increase), the performance improvement will arise.

[haraken, 2015-08-24 06:53:31]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2015-08-24 06:53:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311683002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311683002/1

[commit-bot: I haz the power, 2015-08-24 08:21:50]

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

[commit-bot: I haz the power, 2015-08-24 08:21:50]

Try jobs failed on following builders:
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[haraken, 2015-08-24 08:23:25]

The CQ bit was checked by haraken@chromium.org

[commit-bot: I haz the power, 2015-08-24 08:23:34]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1311683002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1311683002/1

[commit-bot: I haz the power, 2015-08-24 09:09:48]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201053