Revert of Roll GN (via buildtools) 321178:326666

Revert of Roll GN (via buildtools) 321178:326666 (patchset #2 id:20001 of https://codereview.chromium.org/1082813004/)

Reason for revert:
Caused gyp_flag_compare failure on Linux GN bots.

BUG=480739
Original issue's description:
> Roll GN (via buildtools) 321178:326666
>
> This picks up the changes for 'gn help all' and
> the markdown docs, fixes a bug related to the
> transitive propagation of public_deps across
> shared objects, and includes a speculative fix
> for the WriteFile() failures we're seeing on
> Windows.
>
> TBR=brettw@chromium.org
>
> Committed: https://crrev.com/a21c4f2acc0b7b97a65c3c145361aed55c53f769
> Cr-Commit-Position: refs/heads/master@{#326704}

TBR=brettw@chromium.org,dpranke@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/e034cea5750b3f2e71d8e628263c39aa568d3f74
Cr-Commit-Position: refs/heads/master@{#326716}

[horo, 2015-04-24 01:37:04]

Created Revert of Roll GN (via buildtools) 321178:326666

[commit-bot: I haz the power, 2015-04-24 01:37:39]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1095553006/1

[commit-bot: I haz the power, 2015-04-24 01:38:29]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-24 01:39:18]

Patchset 1 (id:??) landed as
https://crrev.com/e034cea5750b3f2e71d8e628263c39aa568d3f74
Cr-Commit-Position: refs/heads/master@{#326716}