[DevTools] Fix one more backwards compatibility breakage.

[DevTools] Fix one more backwards compatibility breakage.

With recent changes, it's dangerous to inject /deep/ selectors
to the page, as they get high priority. This patch stops injecting
backwards compatilibity code to the all-new frontned.

BUG=none

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=201106

[dgozman, 2015-08-25 00:49:08]

dgozman@chromium.org changed reviewers:
+ pfeldman@chromium.org

[dgozman, 2015-08-25 00:49:09]

Take a look please.

[pfeldman, 2015-08-25 00:53:55]

The CQ bit was checked by pfeldman@chromium.org

[pfeldman, 2015-08-25 00:53:56]

lgtm

[commit-bot: I haz the power, 2015-08-25 00:54:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310653003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310653003/1

[commit-bot: I haz the power, 2015-08-25 02:05:46]

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

[commit-bot: I haz the power, 2015-08-25 02:05:47]

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

[dgozman, 2015-08-25 05:11:22]

The CQ bit was checked by dgozman@chromium.org

[commit-bot: I haz the power, 2015-08-25 05:11:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1310653003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1310653003/1

[commit-bot: I haz the power, 2015-08-25 05:44:31]

Committed patchset #1 (id:1) as
https://src.chromium.org/viewvc/blink?view=rev&revision=201106