Roll GN binaries to r307979 to get the new default logic.

Roll GN binaries to r307979 to get the new default logic.

This will allow us to specify which binaries are built by
default by changing what is declared in a group("default")
target in src/BUILD.gn (this was added in r307770).

This rolls buildtools to 4995faa.

TBR=scottmg@chromium.org, brettw@chromium.org
BUG=430215
Committed: https://crrev.com/a4a492b196181beb7c9253ce95a1d6239e1709e9
Cr-Commit-Position: refs/heads/master@{#308050}

[Dirk Pranke, 2014-12-12 02:41:36]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2014-12-12 02:43:05]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/801623002/1

[scottmg, 2014-12-12 03:38:10]

lgtm

[commit-bot: I haz the power, 2014-12-12 04:36:11]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-12 04:36:56]

Patchset 1 (id:??) landed as
https://crrev.com/a4a492b196181beb7c9253ce95a1d6239e1709e9
Cr-Commit-Position: refs/heads/master@{#308050}