Fix gn check errors for cc/blink

Fix gn check errors for cc/blink

Once blink headers are added as sources (https://codereview.chromium.org/1222673004/), if you run the following
command line, you will get errors like this:

$ gn check
ERROR at //cc/blink/web_layer_impl_fixed_bounds_unittest.cc:13:11: Can't include this header from here.
          ^-------------------------------------------------
The target:
  //cc/blink:_cc_blink_unittests__library
is including a file from the target:
  //third_party/WebKit/public:blink_headers

It's usually best to depend directly on the destination target.
In some cases, the destination target is considered a subcomponent
of an intermediate target. In this case, the intermediate target
should depend publicly on the destination to forward the ability
to include headers.

Dependency chain (there may also be others):
  //cc/blink:_cc_blink_unittests__library -->
  //cc/blink:blink --[private]-->
  //third_party/WebKit/public:blink -->
  //third_party/WebKit/public:blink_headers

BUG=367595
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Committed: https://crrev.com/b11fbc239c0aa61b0110cd52939ea66ba545586a
Cr-Commit-Position: refs/heads/master@{#337744}

[agrieve, 2015-07-04 02:30:26]

agrieve@chromium.org changed reviewers:
+ brettw@chromium.org

[brettw, 2015-07-07 21:53:27]

lgtm

[agrieve, 2015-07-07 23:35:36]

The CQ bit was checked by agrieve@chromium.org

[commit-bot: I haz the power, 2015-07-07 23:40:24]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1216083003/1

[commit-bot: I haz the power, 2015-07-08 02:26:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-08 02:27:00]

Patchset 1 (id:??) landed as
https://crrev.com/b11fbc239c0aa61b0110cd52939ea66ba545586a
Cr-Commit-Position: refs/heads/master@{#337744}