Expanded code in CompareCSSValuePtr to be more readable

Expanded code in CompareCSSValuePtr to be more readable

Expanded the ternary operator in CSSValuePtr to a set of if-statements
that are much more readable. This code was previously difficult to
understand and this change should not noticeably affect performance
(this code is not part of a performance-critical path).

For more info, see this doc:
https://docs.google.com/document/d/1srJG5_Obcmty8NlsTNMJiYhVZlMdmzASWJHPnIQNB0I/edit

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=197496

[sashab, 2015-06-19 18:43:30]

sashab@chromium.org changed reviewers:
+ esprehn@chromium.org, timloh@chromium.org

[esprehn, 2015-06-19 18:46:41]

lgtm, down with the ternaries!

[esprehn, 2015-06-19 18:47:06]

The CQ bit was checked by esprehn@chromium.org

[commit-bot: I haz the power, 2015-06-19 18:47:31]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1194073002/1

[commit-bot: I haz the power, 2015-06-19 20:13:54]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=197496