Add MD Ink Drop to host only when a ripple/hover is active.

Add MD Ink Drop to host only when a ripple/hover is active.

In order to paint the material design ink drop behind button icons the icon View
and the button View have to paint to their own Layers. There is no need to incur
the additional expense of these Layers unless the ink drop ripple or hover is
actually active on the View.

BUG=604415
TEST=InkDropHoverTest.*
TEST=InkDropAnimationControllerImplTest.*
TEST=InkDropAnimationControllerFactoryTest.VerifyInkDropLayersRemovedAfterDestructionWhenHoverIsActive

Review-Url: https://codereview.chromium.org/1897073002
Cr-Commit-Position: refs/heads/master@{#390696}
(cherry picked from commit 741be72a4d24789a876d87d0d94e9e2e1cdcd674)

Committed: https://chromium.googlesource.com/chromium/src/+/b597394a728de58aca50b199fa08b61787426682

[bruthig, 2016-05-03 21:48:08]

Description was changed from

==========
Add MD Ink Drop to host only when a ripple/hover is active.

In order to paint the material design ink drop behind button icons the icon View
and the button View have to paint to their own Layers. There is no need to incur
the additional expense of these Layers unless the ink drop ripple or hover is
actually active on the View.

BUG=604415

TEST=InkDropHoverTest.*
TEST=InkDropAnimationControllerImplTest.*
TEST=InkDropAnimationControllerFactoryTest.VerifyInkDropLayersRemovedAfterDestructionWhenHoverIsActive

Review-Url: https://codereview.chromium.org/1897073002
Cr-Commit-Position: refs/heads/master@{#390696}
(cherry picked from commit 741be72a4d24789a876d87d0d94e9e2e1cdcd674)
==========

to

==========
Add MD Ink Drop to host only when a ripple/hover is active.

In order to paint the material design ink drop behind button icons the icon View
and the button View have to paint to their own Layers. There is no need to incur
the additional expense of these Layers unless the ink drop ripple or hover is
actually active on the View.

BUG=604415

TEST=InkDropHoverTest.*
TEST=InkDropAnimationControllerImplTest.*
TEST=InkDropAnimationControllerFactoryTest.VerifyInkDropLayersRemovedAfterDestructionWhenHoverIsActive

Review-Url: https://codereview.chromium.org/1897073002
Cr-Commit-Position: refs/heads/master@{#390696}
(cherry picked from commit 741be72a4d24789a876d87d0d94e9e2e1cdcd674)

Committed:
https://chromium.googlesource.com/chromium/src/+/b597394a728de58aca50b199fa08...
==========

[bruthig, 2016-05-03 21:48:16]

Committed patchset #2 (id:20001) manually as
b597394a728de58aca50b199fa08b61787426682.