[strong] weak classes can't inherit from strong ones

[strong] weak classes can't inherit from strong ones

Prerequisite for sealing strong class instances.

Depends on https://codereview.chromium.org/1314203002/

BUG=v8:3956
LOG=N

Committed: https://crrev.com/db440dfe8d776ca3f0a5a21f6cfce070814649c5
Cr-Commit-Position: refs/heads/master@{#30541}

[conradw, 2015-09-02 08:44:55]

conradw@chromium.org changed reviewers:
+ bmeurer@chromium.org, rossberg@chromium.org

[conradw, 2015-09-02 08:44:56]

PTAL

[Benedikt Meurer, 2015-09-02 11:03:56]

LGTM!

[conradw, 2015-09-02 11:28:56]

The CQ bit was checked by conradw@chromium.org

[conradw, 2015-09-02 11:28:57]

The patchset sent to the CQ was uploaded after l-g-t-m from bmeurer@chromium.org
Link to the patchset: https://codereview.chromium.org/1316333002/#ps80001
(title: "minor comment reorder")

[commit-bot: I haz the power, 2015-09-02 11:29:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1316333002/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1316333002/80001

[commit-bot: I haz the power, 2015-09-02 11:36:11]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-09-02 11:36:28]

Patchset 5 (id:??) landed as
https://crrev.com/db440dfe8d776ca3f0a5a21f6cfce070814649c5
Cr-Commit-Position: refs/heads/master@{#30541}