Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash  by replacing DCHECK in Node::mutableComputedStyle with returning nullptr if the NodeRareData is not an ElementRareData.

Crash introcuded in https://codereview.chromium.org/1962953002.

BUG=638102
Committed: https://crrev.com/c739b16ff7c5b84fcd4620df5d46c419563c2ef7
Cr-Commit-Position: refs/heads/master@{#412472}

[Bugs Nash, 2016-08-16 23:30:56]

The CQ bit was checked by bugsnash@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-16 23:32:01]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[Bugs Nash, 2016-08-16 23:33:21]

bugsnash@chromium.org changed reviewers:
+ rjwright@chromium.org

[Bugs Nash, 2016-08-16 23:34:10]

bugsnash@chromium.org changed reviewers:
+ esprehn@chromium.org

[commit-bot: I haz the power, 2016-08-17 01:02:35]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-17 01:02:37]

Dry run: Exceeded global retry quota

[rjwright, 2016-08-17 03:32:20]

lgtm

[Timothy Loh, 2016-08-17 03:33:10]

Test? :)

[Bugs Nash, 2016-08-17 04:04:01]

Description was changed from

==========
Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash  by replacing DCHECK in Node::mutableComputedStyle with returning
nullptr if the NodeRareData is not an ElementRareData.

BUG=638102
==========

to

==========
Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash  by replacing DCHECK in Node::mutableComputedStyle with returning
nullptr if the NodeRareData is not an ElementRareData.

Crash introcuded in https://codereview.chromium.org/1962953002.

BUG=638102
==========

[Bugs Nash, 2016-08-17 04:29:21]

On 2016/08/17 at 03:33:10, timloh wrote:
> Test? :)

Added, thanks

[Bugs Nash, 2016-08-17 04:32:26]

The CQ bit was checked by bugsnash@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-17 04:32:43]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[esprehn, 2016-08-17 04:48:21]

Lgtm, glad we caught this :)

I'm worried about the amount of branching we've introduced here in general. We
probably want to figure out how to simplify this down but it's fine to start
here.

[commit-bot: I haz the power, 2016-08-17 05:44:55]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-08-17 05:44:56]

Dry run: This issue passed the CQ dry run.

[Bugs Nash, 2016-08-17 08:00:01]

The CQ bit was checked by bugsnash@chromium.org

[Bugs Nash, 2016-08-17 08:00:02]

The patchset sent to the CQ was uploaded after l-g-t-m from
rjwright@chromium.org
Link to the patchset: https://codereview.chromium.org/2241193005/#ps20001
(title: "Added layout test")

[commit-bot: I haz the power, 2016-08-17 08:00:21]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-17 08:04:24]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-08-17 08:14:23]

Description was changed from

==========
Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash  by replacing DCHECK in Node::mutableComputedStyle with returning
nullptr if the NodeRareData is not an ElementRareData.

Crash introcuded in https://codereview.chromium.org/1962953002.

BUG=638102
==========

to

==========
Fixed crash by replacing DCHECK with returning nullptr.

Fixed crash  by replacing DCHECK in Node::mutableComputedStyle with returning
nullptr if the NodeRareData is not an ElementRareData.

Crash introcuded in https://codereview.chromium.org/1962953002.

BUG=638102

Committed: https://crrev.com/c739b16ff7c5b84fcd4620df5d46c419563c2ef7
Cr-Commit-Position: refs/heads/master@{#412472}
==========

[commit-bot: I haz the power, 2016-08-17 08:14:24]

Patchset 2 (id:??) landed as
https://crrev.com/c739b16ff7c5b84fcd4620df5d46c419563c2ef7
Cr-Commit-Position: refs/heads/master@{#412472}