Add flag to force complex text for tests

Add flag to force complex text for tests

Add --always-use-complex-text flag to content_shell to force the use of
the complex text path for layout tests. Thus allowing us to selectively
enabled it on a per directory basis for layout tests, instead of having
to rebaseline every single test at once.

This is a temporary flag that will be removed once AlwaysUseComplexText
runtime enabled feature has been enabled.

BUG=404597
R=mkwst@chromium.org, drott@chromium.org

Committed: https://crrev.com/81407eee8b5049cd7accf436293a8a003ddd2b65
Cr-Commit-Position: refs/heads/master@{#353528}

[eae, 2015-10-12 11:18:40]

eae@chromium.org changed reviewers:
+ drott@chromium.org, mkwst@chromium.org

[drott, 2015-10-12 11:24:36]

LGTM for WebKit/*

[eae, 2015-10-12 11:25:09]

Mike: please review the content/ changes
Dominik: please review webkit/ changes

[Mike West, 2015-10-12 11:43:41]

//content/shell LGTM.

[eae, 2015-10-12 11:45:18]

Thanks!

[eae, 2015-10-12 11:45:26]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2015-10-12 11:46:01]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1394003004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1394003004/1

[commit-bot: I haz the power, 2015-10-12 14:09:16]

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

[commit-bot: I haz the power, 2015-10-12 14:09:17]

Try jobs failed on following builders:
  linux_android_rel_ng on tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_android_r...)

[eae, 2015-10-12 14:38:36]

The CQ bit was checked by eae@chromium.org

[commit-bot: I haz the power, 2015-10-12 14:38:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1394003004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1394003004/1

[tandrii(chromium), 2015-10-12 14:59:05]

The CQ bit was unchecked by tandrii@chromium.org

[tandrii(chromium), 2015-10-12 15:00:59]

The CQ bit was checked by tandrii@chromium.org

[commit-bot: I haz the power, 2015-10-12 15:04:14]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1394003004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1394003004/1

[commit-bot: I haz the power, 2015-10-12 16:12:44]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-12 16:13:30]

Patchset 1 (id:??) landed as
https://crrev.com/81407eee8b5049cd7accf436293a8a003ddd2b65
Cr-Commit-Position: refs/heads/master@{#353528}