Remove bogus ASSERT(frame) from RenderObject::willBeDestroyed

This ASSERT was added way back in http://trac.webkit.org/changeset/48070 but
is false in practice (see attached bug). Given that we already handle frame-nullity
in this method, I don't see a reason to carry this legacy ASSERT around with us.

R=eae@chromium.org
BUG=308786

Review URL: https://codereview.chromium.org/35153004

git-svn-id: svn://svn.chromium.org/blink/trunk@160247 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Revert "Remove redundant checks from SharedStyleFinder::canShareStyleWithElement"

This reverts commit 481c9bfa6a21d9f1bcf9610820e2465c02c76173.

BUG=310266
TBR=esprehn@chromium.org,eseidel@chromium.org
NOTRY=true

Review URL: https://codereview.chromium.org/34623006

git-svn-id: svn://svn.chromium.org/blink/trunk@160248 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove some dead code.

NOTRY=true

Review URL: https://codereview.chromium.org/35903002

git-svn-id: svn://svn.chromium.org/blink/trunk@160249 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Fix tracking of the id attribute string if it is shared across elements.

The patch to remove AtomicStringImpl:
http://src.chromium.org/viewvc/blink?view=rev&rev=154790

Exposed a lifetime issue with strings for id attributes. We simply need to use
AtomicString.

BUG=290566

Review URL: https://codereview.chromium.org/33793004

git-svn-id: svn://svn.chromium.org/blink/trunk@160250 bbb929c8-8fbe-4397-9dbb-9b2b20218538