Convert RenderFlexibleBox code to use RenderBox references

Convert RenderFlexibleBox code to use RenderBox references

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.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=181787

[Sunil Ratnu, 2014-09-09 20:08:01]

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

[Sunil Ratnu, 2014-09-09 20:08:01]

I will completely convert the code to use references soon in a later patch.
Please review this. Thanks!

[cbiesinger, 2014-09-09 20:40:46]

lgtm

[Sunil Ratnu, 2014-09-10 02:38:33]

@leviw: owner's LGTM required. Please review this. Thanks!

[Sunil Ratnu, 2014-09-10 06:12:23]

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

[Sunil Ratnu, 2014-09-10 08:56:52]

For reference: Here's the second part of this change:
https://codereview.chromium.org/560583003/

[esprehn, 2014-09-11 01:12:58]

sigh, references make all the call sites so ugly with stars :(

lgtm

[Sunil Ratnu, 2014-09-11 02:48:18]

On 2014/09/11 01:12:58, esprehn wrote:
> sigh, references make all the call sites so ugly with stars :(
> 
> lgtm

The second patch where almost all methods have been totally converted, makes
atleast some call sites again look better. :)

[Sunil Ratnu, 2014-09-11 02:48:34]

The CQ bit was checked by sunil.ratnu@samsung.com

[commit-bot: I haz the power, 2014-09-11 02:48:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/555213002/1

[commit-bot: I haz the power, 2014-09-11 03:35:11]

Committed patchset #1 (id:1) as 181787