Enable some ServiceWorker layout tests

http/tests/serviceworker/registration.html
* was waiting on CR side to land

virtual/serviceworker/http/tests/serviceworker/registration.html
* was crashy but seems okay now (?)

virtual/serviceworker/http/tests/serviceworker/indexeddb.html
virtual/serviceworker/http/tests/serviceworker/postmessage.html
* were waiting on CR side to land

BUG=350103,352703,285976
TBR=alecflett

Review URL: https://codereview.chromium.org/210473003

git-svn-id: svn://svn.chromium.org/blink/trunk@169890 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove PostAttachCallbacks and replace with something more specialized

The last consumer of PostAttachCallbacks is layer updating, this patch
switches away from the generic "call me after recalc style" system that
was PostAttachCallbacks to a very specialized system that only marks
elements as needing a style recalc for the purposes of creating and
destroying layers.

Review URL: https://codereview.chromium.org/143983007

git-svn-id: svn://svn.chromium.org/blink/trunk@169891 bbb929c8-8fbe-4397-9dbb-9b2b20218538