Revert of [swarming] Isolate v8 testing.

Revert of [swarming] Isolate v8 testing. (patchset #8 id:140001 of https://codereview.chromium.org/1380593002/ )

Reason for revert:
Prime suspect in breakage of V8 Linux -- no snap

Original issue's description:
> [swarming] Isolate v8 testing.
>
> Add gyp support and isolates for default test suites.
> Add two default isolates, one (default) for using the
> test suite collection we call "default" on the bots. One
> (developer_default) for also supporting the way developers
> call the driver (i.e. without argument, which includes
> the unittests).
>
> BUG=chromium:535160
> LOG=n
>
> Committed: https://crrev.com/9bd83f58f29ab0c7c5b71b00bcb1df3a9e641f05
> Cr-Commit-Position: refs/heads/master@{#31081}

TBR=tandrii@chromium.org,jochen@chromium.org,maruel@chromium.org,machenbach@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=chromium:535160
Committed: https://crrev.com/280a6f8ec84327692a4dedf4edc1ea72f5d5ba73
Cr-Commit-Position: refs/heads/master@{#31084}

[danno, 2015-10-02 15:44:35]

Created Revert of [swarming] Isolate v8 testing.

[commit-bot: I haz the power, 2015-10-02 15:44:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1370993008/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1370993008/1

[commit-bot: I haz the power, 2015-10-02 15:45:08]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-10-02 15:45:36]

Patchset 1 (id:??) landed as
https://crrev.com/280a6f8ec84327692a4dedf4edc1ea72f5d5ba73
Cr-Commit-Position: refs/heads/master@{#31084}

[Michael Achenbach, 2015-10-02 17:40:36]

lgtm, thanks for reverting. Looks like external_startup_data is also 1 in nosnap
builds - where there's no startup data. Will add and extra condition...