CC Animations: Establish AnimationHost, AnimationTimeline and AnimationPlayer.

The compositor should not need to worry about servicing animations.
Instead, it should be able to request property updates as needed from external
mutators.

- We setup CC representations for blink::AnimationPlayer and blink::AnimationTimeline.
- We want to move all the animation-related code from LayerTreeHost to AnimationHost.
- We move LayerAnimatedController ownership to cc::AnimationPlayer.
- We move AnimationRegistrar ownership to cc::AnimationHost.
- We add/remove animations to cc::AnimationPlayer from now.
- LayerAnimatedController to be merged into cc::AnimaitonPlayer.
- AnimationRegistrar to be merged into cc::AnimationHost/cc::AnimationTimeline.

A chromium part. Blink part: https://codereview.chromium.org/946323002

Next episode:
https://codereview.chromium.org/1010663002/

BUG=394777
R=dstockwell@chromium.org
R=shane@chromium.org
R=ajuma@chromium.org
R=vollick@chromium.org
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/947033002

Cr-Commit-Position: refs/heads/master@{#337266}

• cc/BUILD.gn[diff]
• cc/animation/animation_host.cc[Added - diff]
• cc/animation/animation_host.h[Added - diff]
• cc/animation/animation_host_unittest.cc[Added - diff]
• cc/animation/animation_id_provider.cc[diff]
• cc/animation/animation_id_provider.h[diff]
• cc/animation/animation_player.cc[Added - diff]
• cc/animation/animation_player.h[Added - diff]
• cc/animation/animation_player_unittest.cc[Added - diff]
• cc/animation/animation_timeline.cc[Added - diff]
• cc/animation/animation_timeline.h[Added - diff]
• cc/animation/animation_timeline_unittest.cc[Added - diff]
• cc/animation/element_animations.cc[Added - diff]
• cc/animation/element_animations.h[Added - diff]
• cc/animation/element_animations_unittest.cc[Added - diff]
• cc/blink/BUILD.gn[diff]
• cc/blink/cc_blink.gyp[diff]
• cc/blink/web_compositor_animation_player_impl.cc[Added - diff]
• cc/blink/web_compositor_animation_player_impl.h[Added - diff]
• cc/blink/web_compositor_animation_timeline_impl.cc[Added - diff]
• cc/blink/web_compositor_animation_timeline_impl.h[Added - diff]
• cc/blink/web_compositor_support_impl.cc[diff]
• cc/blink/web_compositor_support_impl.h[diff]
• cc/cc.gyp[diff]
• cc/cc_tests.gyp[diff]
• cc/layers/layer.cc[diff]
• cc/test/animation_test_common.cc[diff]
• cc/test/animation_test_common.h[diff]
• cc/test/animation_timelines_test_common.cc[Added - diff]
• cc/test/animation_timelines_test_common.h[Added - diff]
• cc/trees/layer_tree_host.cc[diff]
• cc/trees/layer_tree_host.h[diff]
• cc/trees/layer_tree_host_impl.cc[diff]
• cc/trees/layer_tree_host_impl.h[diff]
• cc/trees/layer_tree_impl.cc[diff]
• cc/trees/layer_tree_impl.h[diff]
• cc/trees/mutator_host_client.h[Added - diff]
• content/renderer/gpu/render_widget_compositor.cc[diff]
• content/renderer/gpu/render_widget_compositor.h[diff]