Use more RenderBox references in RenderFlexibleBox

Use more RenderBox references in RenderFlexibleBox

RenderFlexibleBox has several methods that take pointers to RenderBox instances
but those methods assumes that the objects will never be NULL. We should replace
them by references. This makes the caller code safer.

This is in continuation to the CL https://codereview.chromium.org/555213002/

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181922

[Sunil Ratnu, 2014-09-10 08:55:29]

sunil.ratnu@samsung.com changed reviewers:
+ cbiesinger@chromium.org, esprehn@chromium.org, leviw@chromium.org

[Sunil Ratnu, 2014-09-10 08:55:29]

This is in continuation and is on top of the CL
https://codereview.chromium.org/555213002/ .

Lets not have a lot of changes into just 1 CL (and also pointer to ref has to be
done carefully), so it was better to split it into two CLs.

Please review this.

[Sunil Ratnu, 2014-09-11 04:30:19]

Since the previous CL https://codereview.chromium.org/555213002/ has already
landed, so rebased it to to the latest master now. Please have a look. Thanks!

[cbiesinger, 2014-09-11 06:17:14]

lgtm

[Sunil Ratnu, 2014-09-11 06:22:49]

Thanks for the review Christian.
@owners: Please take a look. Thanks!

[Sunil Ratnu, 2014-09-12 00:35:41]

On 2014/09/11 06:22:49, Sunil Ratnu wrote:
> Thanks for the review Christian.
> @owners: Please take a look. Thanks!

Owners LGTM required. Please take a look. Thanks!

[leviw_travelin_and_unemployed, 2014-09-12 18:08:08]

rslgtm

[leviw_travelin_and_unemployed, 2014-09-12 18:08:29]

The CQ bit was checked by leviw@chromium.org

[leviw_travelin_and_unemployed, 2014-09-12 18:08:30]

lgtm

[commit-bot: I haz the power, 2014-09-12 18:09:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/560583003/20001

[commit-bot: I haz the power, 2014-09-12 18:31:16]

Committed patchset #2 (id:20001) as 181922