Change StyleBuilderConverter functions to take const CSSValue&s

Change StyleBuilderConverter functions to take const CSSValue&s

Change StyleBuilderConverter functions to take const CSSValue&s instead
of CSSValue*s. Since these values can never be null, this makes the code
easier to work with.

BUG=526586
Committed: https://crrev.com/fdc999369aacd205cb488708de7623e6079e51ac
Cr-Commit-Position: refs/heads/master@{#353243}

[sashab, 2015-10-02 05:07:01]

Patchset #2 (id:20001) has been deleted

[sashab, 2015-10-07 06:20:22]

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

[sashab, 2015-10-07 06:20:23]

No const_cast<>s needed! :D

[Timothy Loh, 2015-10-08 00:16:30]

lgtm

[sashab, 2015-10-08 04:58:24]

The CQ bit was checked by sashab@chromium.org

[commit-bot: I haz the power, 2015-10-08 04:58:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1377943005/60001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1377943005/60001

[commit-bot: I haz the power, 2015-10-08 05:00:05]

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

[commit-bot: I haz the power, 2015-10-08 05:00:05]

Try jobs failed on following builders:
  mac_chromium_compile_dbg_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_comp...)
  mac_chromium_gn_rel on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_gn_r...)
  mac_chromium_rel_ng on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/mac_chromium_rel_...)

[sashab, 2015-10-09 05:35:48]

The CQ bit was checked by sashab@chromium.org

[sashab, 2015-10-09 05:35:48]

The patchset sent to the CQ was uploaded after l-g-t-m from timloh@chromium.org
Link to the patchset: https://codereview.chromium.org/1377943005/#ps80001
(title: "Rebase")

[commit-bot: I haz the power, 2015-10-09 05:36:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1377943005/80001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1377943005/80001

[commit-bot: I haz the power, 2015-10-09 07:18:08]

Committed patchset #4 (id:80001)

[commit-bot: I haz the power, 2015-10-09 07:19:49]

Patchset 4 (id:??) landed as
https://crrev.com/fdc999369aacd205cb488708de7623e6079e51ac
Cr-Commit-Position: refs/heads/master@{#353243}