Revert of Add gclient hook to download prebuilt mojo_shell

Revert of Add gclient hook to download prebuilt mojo_shell (patchset #7 id:120001 of https://codereview.chromium.org/667853002/)

Reason for revert:
gclient sync fails to execute download_shell_binary.py

Original issue's description:
> Add gclient hook to download prebuilt mojo_shell
>
> This adds a gclient hook that downloads prebuilt mojo_shell binaries
> from google storage (linux only for now) and gyp/gn flags to toggle
> using these prebuilt binaries instead of ones built from source. This
> also adds a helper script that uploads a locally built mojo_shell binary
> to the appropriate place in google storage.  The versioning scheme is:
>
> *) mojo/public/VERSION contains an identifier (committish currently) for
>   the mojo public SDK. The mojo_shell binary must match the interfaces
>   defined in this version of mojo/public/.
>
> *) gs://mojo/shell/$VERSION/$PLATFORM.zip contains a prebuilt mojo_shell
>   binary for a particular version. $PLATFORM for now must be linux-x64,
>   but we can add more later as needed.
>
> gclient runhooks downloads the shell binary referred to by
> mojo/public/VERSION if it is available for the host platform to
> mojo/public/tools/prebuilt/ and updates mojo/public/tools/prebuilt/VERSION
> to tag the version downloaded if successful. On subsequent runs the hook
> will check this against mojo/public/VERSION and avoid downloading again if
> the binary is up to date.
>
> This also adds variables to the GYP and GN builds that control if building
> 'mojo' builds a mojo_shell binary from source or copies the prebuilt binary
> into the outdir.  They both default to false for now.
>
> R=abarth@chromium.org
>
> Committed: https://crrev.com/e098527822f3e25fb5b86c1441f7ce6e4c2cfdc8
> Cr-Commit-Position: refs/heads/master@{#300600}

TBR=abarth@chromium.org,jamesr@chromium.org
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/a1db3b6db55da85ff4278d7704cfdaa32e9ea92f
Cr-Commit-Position: refs/heads/master@{#300637}

[yurys, 2014-10-22 05:23:03]

Created Revert of Add gclient hook to download prebuilt mojo_shell

[commit-bot: I haz the power, 2014-10-22 05:24:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/670073002/1

[yurys, 2014-10-22 05:24:16]

The CQ bit was unchecked by yurys@chromium.org

[commit-bot: I haz the power, 2014-10-22 05:24:21]

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

[yurys, 2014-10-22 05:28:23]

The CQ bit was checked by yurys@chromium.org

[yurys, 2014-10-22 05:28:52]

The CQ bit was unchecked by yurys@chromium.org

[yurys, 2014-10-22 05:31:12]

The CQ bit was checked by yurys@chromium.org

[commit-bot: I haz the power, 2014-10-22 05:32:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/670073002/1

[commit-bot: I haz the power, 2014-10-22 05:32:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-22 05:33:54]

Patchset 1 (id:??) landed as
https://crrev.com/a1db3b6db55da85ff4278d7704cfdaa32e9ea92f
Cr-Commit-Position: refs/heads/master@{#300637}