cc: Make LayerAnimationController keep state for clearing scroll delta

cc: Make LayerAnimationController keep state for clearing scroll delta

When a scroll offset animation is removed, the corresponding LayerImpl's
scroll delta needs to be cleared at activation. This CL moves the state
tracking whether such clearing is needed from LayerImpl to
LayerAnimationController, since this behavior is intended to be specific
to this use case rather than providing a general way to clear scroll
deltas.

BUG=243871
Committed: https://crrev.com/4256b4582ef4d1f257320452d445395610ed6ac4
Cr-Commit-Position: refs/heads/master@{#312609}

[ajuma, 2015-01-21 16:38:41]

ajuma@chromium.org changed reviewers:
+ aelias@chromium.org, vollick@chromium.org

[aelias_OOO_until_Jul13, 2015-01-21 21:23:52]

Looks OK, just some minor comments:

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
File cc/animation/layer_animation_controller.h (right):

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
cc/animation/layer_animation_controller.h:142: // When a scroll animation is
removed on the main thread, its compositor
I'd add the comment "This is to provide the illusion of synchronicity to JS that
simultaneously removes an animation and sets the scroll offset."

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
cc/animation/layer_animation_controller.h:148: bool
clear_scroll_delta_for_removed_animation() const {
Could you rename this and the field to "animation_was_interrupted"?  I'd rather
be declarative rather than imperative in the naming, it's the layer's job to
decide what to do as a result of the removed animation (and maybe we'll come up
with a different policy on this at some point).

[ajuma, 2015-01-21 21:50:27]

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
File cc/animation/layer_animation_controller.h (right):

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
cc/animation/layer_animation_controller.h:142: // When a scroll animation is
removed on the main thread, its compositor
On 2015/01/21 21:23:52, aelias wrote:
> I'd add the comment "This is to provide the illusion of synchronicity to JS
that
> simultaneously removes an animation and sets the scroll offset."

Done.

https://codereview.chromium.org/864003002/diff/20001/cc/animation/layer_anima...
cc/animation/layer_animation_controller.h:148: bool
clear_scroll_delta_for_removed_animation() const {
On 2015/01/21 21:23:52, aelias wrote:
> Could you rename this and the field to "animation_was_interrupted"?  I'd
rather
> be declarative rather than imperative in the naming, it's the layer's job to
> decide what to do as a result of the removed animation (and maybe we'll come
up
> with a different policy on this at some point).

Done.

[aelias_OOO_until_Jul13, 2015-01-21 23:29:15]

lgtm, thanks.

[ajuma, 2015-01-22 14:10:16]

The CQ bit was checked by ajuma@chromium.org

[commit-bot: I haz the power, 2015-01-22 14:10:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/864003002/40001

[commit-bot: I haz the power, 2015-01-22 14:29:25]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-01-22 14:30:17]

Patchset 3 (id:??) landed as
https://crrev.com/4256b4582ef4d1f257320452d445395610ed6ac4
Cr-Commit-Position: refs/heads/master@{#312609}