Don't allow style sharing between top layer and non-top layer elements

Don't allow style sharing between top layer and non-top layer elements

Normally, top layer elements are ensured a layer in adjustRenderStyle.
However, if style sharing occurs, the top layer element can receive a style
that causes it to not have a layer, which will break top layer rendering.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=166215

[falken, 2014-01-31 07:26:30]

morrita@: r?

[hayato, 2014-01-31 08:13:35]

LGTM.

[Hajime Morrita, 2014-01-31 08:14:03]

lgtm. @ojan an @esprehn may have some opinion in this area.

[commit-bot: I haz the power, 2014-01-31 08:14:10]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/falken@chromium.org/150273003/1

[commit-bot: I haz the power, 2014-01-31 10:59:53]

Retried try job too often on linux_blink for step(s) webkit_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=linux_blin...

[commit-bot: I haz the power, 2014-01-31 10:59:55]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 10:59:59]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 11:04:21]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/falken@chromium.org/150273003/1

[commit-bot: I haz the power, 2014-01-31 14:23:14]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 14:23:14]

CQ bit was unchecked on CL. Ignoring.

[commit-bot: I haz the power, 2014-01-31 14:23:14]

Change committed as 166215

[commit-bot: I haz the power, 2014-01-31 14:23:17]

CQ bit was unchecked on CL. Ignoring.