[Effen] Add AnimatedComponent base class

[Effen] Add AnimatedComponent base class

This patch adds a base AnimatedComponent from which most components that animated should derive. It takes care of listening & unlistening from the animations during did(Un)mount as well as binding the animated value to a private field and scheduling the component for build.

Note that this patch removes the did(Un)mount overridable methods from Component and replaces them with a callback mechanism which is less brittle.

BUG=
R=abarth@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/465402ea49933d769293b3f657d90219d1ef3c24

[rafaelw, 2015-03-20 05:34:12]

rafaelw@chromium.org changed reviewers:
+ abarth@chromium.org

[rafaelw, 2015-03-20 05:36:00]

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
File sky/framework/animation/animated_value.dart (right):

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
sky/framework/animation/animated_value.dart:16: _value = initial;
Note: this prevents the initial value from being broadcast in the stream.
Consumers are expected to retrieve the initial value via the accessor.

[abarth-chromium, 2015-03-20 05:41:49]

LGTM

That's really slick.

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
File sky/framework/animation/animated_value.dart (right):

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
sky/framework/animation/animated_value.dart:16: _value = initial;
On 2015/03/20 at 05:36:00, rafaelw wrote:
> Note: this prevents the initial value from being broadcast in the stream.
Consumers are expected to retrieve the initial value via the accessor.

Maybe add a comment explaining this subtle point?

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/component...
File sky/framework/components/animated_component.dart (right):

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/component...
sky/framework/components/animated_component.dart:34: }
Wow

[rafaelw, 2015-03-20 05:49:45]

Committed patchset #3 (id:40001) manually as
465402ea49933d769293b3f657d90219d1ef3c24 (presubmit successful).

[rafaelw, 2015-03-20 05:52:31]

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
File sky/framework/animation/animated_value.dart (right):

https://codereview.chromium.org/1027633003/diff/20001/sky/framework/animation...
sky/framework/animation/animated_value.dart:16: _value = initial;
On 2015/03/20 05:41:49, abarth wrote:
> On 2015/03/20 at 05:36:00, rafaelw wrote:
> > Note: this prevents the initial value from being broadcast in the stream.
> Consumers are expected to retrieve the initial value via the accessor.
> 
> Maybe add a comment explaining this subtle point?

Done.