Move LayerTreeHostCommon Copy Request tests to use LayerTreeHostImpl

Move LayerTreeHostCommon Copy Request tests to use LayerTreeHostImpl

LayerTreeHostCommon tests how copy request affects draw by testing
RenderSurfaceLayerList. We are moving RenderSurfaceLayerList generation
to compositor thread only, thus moving these tests to use compositor
thread's testing setup.

Tests changed:
    LayerTreeHostCommonTest.SubtreeHiddenWithCopyRequest
    LayerTreeHostCommonTest.ClippedOutCopyRequest

BUG=502041, 504466
R=enne
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/51fb255dda0cc4ed63d93d90df6e6f288ccfeb06
Cr-Commit-Position: refs/heads/master@{#340279}

[weiliangc, 2015-07-23 21:34:04]

Slightly more complicated but conceptually just s/Layer/LayerImpl/

[enne (OOO), 2015-07-23 22:15:47]

lgtm

[weiliangc, 2015-07-24 15:08:40]

The CQ bit was checked by weiliangc@chromium.org

[commit-bot: I haz the power, 2015-07-24 15:08:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1243373004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1243373004/1

[commit-bot: I haz the power, 2015-07-24 15:32:37]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-24 15:33:29]

Patchset 1 (id:??) landed as
https://crrev.com/51fb255dda0cc4ed63d93d90df6e6f288ccfeb06
Cr-Commit-Position: refs/heads/master@{#340279}