Make d8 default to standard location for external snapshots.

Make d8 default to standard location for external snapshots.

This makes tests runnable with the external snapshot, and should be the
last step before enabling external snapshot on >=1 bots.

R=yangguo
BUG=

[vogelheim, 2014-12-10 15:26:58]

Patchset #1 (id:1) has been deleted

[vogelheim, 2014-12-10 15:29:34]

Patchset #1 (id:20001) has been deleted

[Yang, 2014-12-10 15:57:24]

On 2014/12/10 15:30:15, vogelheim wrote:

lgtm. But for the record, I'd have preferred having the test runner
(test/mjsunit/testcfg) provide the correct command line args instead of
hardcoding them.

[vogelheim, 2014-12-10 16:08:46]

On 2014/12/10 15:57:24, Yang wrote:
> On 2014/12/10 15:30:15, vogelheim wrote:
> 
> lgtm. But for the record, I'd have preferred having the test runner
> (test/mjsunit/testcfg) provide the correct command line args instead of
> hardcoding them.

Ack. I considered that. The reason why I went with this solution was the
prospect of eventually perma-enabling the external snapshot, and then every user
of d8 ever would have to add two command line params every time. That just
sounded super tedious. I did leave in the option of supplying the two blobs
explicitly.

[vogelheim, 2014-12-10 16:08:59]

The CQ bit was checked by vogelheim@chromium.org

[commit-bot: I haz the power, 2014-12-10 16:09:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/780333004/40001

[commit-bot: I haz the power, 2014-12-10 16:36:34]

Committed patchset #1 (id:40001)