Added more constructors to CallbackLayerAnimationObserver.

Added more constructors to CallbackLayerAnimationObserver.

Some clients of the CallbackLayerAnimationObserver might not need
require all callbacks to be notified. This CL adds some new constructors
with default behavior for unspecified callbacks.

TEST=CallbackLayerAnimationObserverDestructionTest.VerifyFalseAutoDelete
TEST=CallbackLayerAnimationObserverDestructionTest.VerifyTrueAutoDelete

Committed: https://crrev.com/a33cc7d19a2c878e2a7d9b4a540d06f3e0c3fc16
Cr-Commit-Position: refs/heads/master@{#354369}

[bruthig, 2015-10-15 20:11:06]

bruthig@chromium.org changed reviewers:
+ ajuma@chromium.org

[bruthig, 2015-10-15 20:11:06]

ajuma@, can you PTAL?

[ajuma, 2015-10-15 20:42:13]

On 2015/10/15 20:11:06, bruthig wrote:
> ajuma@, can you PTAL?

lgtm

[bruthig, 2015-10-15 20:42:48]

The CQ bit was checked by bruthig@chromium.org

[commit-bot: I haz the power, 2015-10-15 20:43:29]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1407043002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1407043002/1

[commit-bot: I haz the power, 2015-10-15 21:47:26]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-15 21:50:21]

Patchset 1 (id:??) landed as
https://crrev.com/a33cc7d19a2c878e2a7d9b4a540d06f3e0c3fc16
Cr-Commit-Position: refs/heads/master@{#354369}