Set use_canvas_skia to 0 when building iOS

Set use_canvas_skia to 0 when building iOS

iOS like Android does not compile render_text.cc used by canvas_skia.cc
so change the value of use_canvas_skia to 0 on that platform to prevent
invisible dependency (currently the linker is removing the methods that
do depends on render_text.cc since they are not used).

BUG=None

Committed: https://crrev.com/48c11af6c797badfc9e8e9e2e48113b2b04ed4b0
Cr-Commit-Position: refs/heads/master@{#323029}

[sdefresne, 2015-03-30 09:46:25]

sdefresne@chromium.org changed reviewers:
+ jochen@chromium.org

[sdefresne, 2015-03-30 09:46:25]

Please take a look.

[jochen (gone - plz use gerrit), 2015-03-31 10:24:54]

lgtm

[sdefresne, 2015-03-31 12:29:23]

The CQ bit was checked by sdefresne@chromium.org

[commit-bot: I haz the power, 2015-03-31 12:29:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1044843002/1

[commit-bot: I haz the power, 2015-03-31 13:51:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-31 13:52:39]

Patchset 1 (id:??) landed as
https://crrev.com/48c11af6c797badfc9e8e9e2e48113b2b04ed4b0
Cr-Commit-Position: refs/heads/master@{#323029}