As the first step in dividing the functionality currently contained in
AnimationPlayer between AnimationPlayer and Animation this patch moves the set
of keyframe properties to the Animation.
These properties are returned from the Animation by a couple of Properties()
methods that provide direct access to the member variable. In future it is
anticipated that the non-const version will be replaced with an appropriate
setter function. This will likely happen when we implement a separate
KeyframeEffect object as defined by the Web Animations API.
With regards to error checking, nsAnimationManager checks the result of
AnimationPlayer::GetSource() and handles the case where it is nullptr.
nsTransitionManager, however, simply asserts that GetSource() is never null much
like it also asserts that there is only one property with one segment in the
animation. Eventually this code should be made more generic which will probably
happen in bug 999927.
This patch makes AnimationPlayers pass their current time down to the Animation
they are playing.
Since all Animations need from their players is their time, this avoids adding
a pointer back to their AnimationPlayer.
