Content Shell: Introduce LayoutTestDevToolsFrontend.

Content Shell: Introduce LayoutTestDevToolsFrontend.

This patch splits out the DRT-specific bits of ShellDevToolsFrontend and
moves them to a new class, which is only instantiated if the flag is set.

BUG=420994
Committed: https://crrev.com/30d20d59838a6d83ec80852e044e4ac1916f51e4
Cr-Commit-Position: refs/heads/master@{#298865}

[Mike West, 2014-10-09 13:14:48]

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

[Mike West, 2014-10-09 13:14:48]

WDYT?

[jochen (gone - plz use gerrit), 2014-10-09 13:16:13]

lgtm

[Mike West, 2014-10-09 13:16:23]

mkwst@chromium.org changed reviewers:
+ peter@chromium.org
- jochen@chromium.org

[Mike West, 2014-10-09 13:16:24]

Peter, since you're interested, want to review this patch?

[Mike West, 2014-10-09 13:19:15]

On 2014/10/09 13:16:24, Mike West wrote:
> Peter, since you're interested, want to review this patch?

Er. Nevermind. Jochen reviewed it less than two minutes after I posted it, while
I was thinking about reassigning. :)

[Mike West, 2014-10-09 13:19:30]

The CQ bit was checked by mkwst@chromium.org

[commit-bot: I haz the power, 2014-10-09 13:19:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/644723002/1

[commit-bot: I haz the power, 2014-10-09 13:33:24]

Committed patchset #1 (id:1) as bf7e0bfa21e3ed52cb874074b114bfe2f4efbe32

[commit-bot: I haz the power, 2014-10-09 13:34:12]

Patchset 1 (id:??) landed as
https://crrev.com/30d20d59838a6d83ec80852e044e4ac1916f51e4
Cr-Commit-Position: refs/heads/master@{#298865}