build/config: No need to handle direct_dependent_configs in GN build.

build/config: No need to handle direct_dependent_configs in GN build.

direct_dependent_configs is the deprecated name for public_configs,
and public_configs is already handled.

gn-dev thread:
https://groups.google.com/a/chromium.org/d/topic/gn-dev/h9N85MIx_Bk/discussion

BUG=None
TEST=gn gen out-gn/Release --args='is_debug=false is_component_build=false symbol_level=1'
R=brettw@chromium.org

Committed: https://crrev.com/65c461c8e9c02230fda24736ef77eedf51fa675c
Cr-Commit-Position: refs/heads/master@{#340524}

[brettw, 2015-07-24 23:36:45]

lgtm

[tfarina, 2015-07-27 18:31:19]

The CQ bit was checked by tfarina@chromium.org

[commit-bot: I haz the power, 2015-07-27 18:33:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1261523002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1261523002/1

[commit-bot: I haz the power, 2015-07-27 19:09:48]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-27 19:10:50]

Patchset 1 (id:??) landed as
https://crrev.com/65c461c8e9c02230fda24736ef77eedf51fa675c
Cr-Commit-Position: refs/heads/master@{#340524}