Add a deprecation message for shadow-piercing descendant combinators and shadow pseudo elements.

Add a deprecation message for shadow-piercing descendant combinators and shadow pseudo elements.

Deprecate /deep/ and '::shadow'.

"Intent to Deprecate" is here: https://groups.google.com/a/chromium.org/forum/#!msg/blink-dev/68qSZM5QMRQ/pT2YCqZSomAJ

Note that there is a plan to support these selectors in the static profile,
however, this is still in the discussion. I'll support these selectors again in the static profile in another patch when the discussion settles down.

This CL deprecates all usages of these selectors, both in the static profile and the dynamic profile.

BUG=489954
Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=196442

[hayato, 2015-06-03 11:49:11]

hayato@chromium.org changed reviewers:
+ esprehn@chromium.org, kochi@chromium.org

[hayato, 2015-06-03 11:49:12]

PTAL

[dglazkov, 2015-06-03 14:42:55]

dglazkov@chromium.org changed reviewers:
+ dglazkov@chromium.org

[dglazkov, 2015-06-03 14:42:56]

lgtm

[hayato, 2015-06-04 00:58:09]

The CQ bit was checked by hayato@chromium.org

[commit-bot: I haz the power, 2015-06-04 00:58:22]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1166833002/40001

[commit-bot: I haz the power, 2015-06-04 01:03:58]

Committed patchset #3 (id:40001) as
https://src.chromium.org/viewvc/blink?view=rev&revision=196442