Fix external-snapshot startup when snapshot is missing, but natives source is available

Fix external-snapshot startup when snapshot is missing, but natives source is available

R=vogelheim@chromium.org
BUG=

Committed: https://crrev.com/1ac47e6138f05cb0950486704eafd66eae75eec4
Cr-Commit-Position: refs/heads/master@{#27573}

[vogelheim, 2015-04-01 17:02:13]

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h
File src/isolate.h (right):

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h#newcode990
src/isolate.h:990: return snapshot_blob_ != NULL && snapshot_blob_->raw_size !=
0;
When does this happen?

I'm a bit surprised. I don't think an embedder should give us an empty snapshot;
they should just not give us a snapshot at all. In the static initialization
case we at least DCHECK for this situation.

ref:
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/snapshot/sn...

[Erik Corry, 2015-04-01 17:07:29]

erik.corry@gmail.com changed reviewers:
+ erik.corry@gmail.com

[Erik Corry, 2015-04-01 17:07:29]

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h
File src/isolate.h (right):

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h#newcode990
src/isolate.h:990: return snapshot_blob_ != NULL && snapshot_blob_->raw_size !=
0;
On 2015/04/01 17:02:13, vogelheim wrote:
> When does this happen?
> 
> I'm a bit surprised. I don't think an embedder should give us an empty
snapshot;
> they should just not give us a snapshot at all. In the static initialization
> case we at least DCHECK for this situation.
> 
> ref:
>
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/snapshot/sn...
> 
This isn't the embedder giving us an empty snapshot, it's our own default
snapshot, which has a null data field.

[vogelheim, 2015-04-01 17:21:09]

lgtm

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h
File src/isolate.h (right):

https://codereview.chromium.org/1049383004/diff/1/src/isolate.h#newcode990
src/isolate.h:990: return snapshot_blob_ != NULL && snapshot_blob_->raw_size !=
0;
On 2015/04/01 17:07:29, Erik Corry wrote:
> On 2015/04/01 17:02:13, vogelheim wrote:
> > When does this happen?
> > 
> > I'm a bit surprised. I don't think an embedder should give us an empty
> snapshot;
> > they should just not give us a snapshot at all. In the static initialization
> > case we at least DCHECK for this situation.
> > 
> > ref:
> >
>
https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/snapshot/sn...
> > 
> This isn't the embedder giving us an empty snapshot, it's our own default
> snapshot, which has a null data field.

Oh. :-(

I guess it shouldn't do that; but since it does we'll need the check.

[Erik Corry Chromium.org, 2015-04-01 17:28:27]

The CQ bit was checked by erikcorry@chromium.org

[commit-bot: I haz the power, 2015-04-01 17:28:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1049383004/1

[commit-bot: I haz the power, 2015-04-01 18:07:36]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-01 18:07:50]

Patchset 1 (id:??) landed as
https://crrev.com/1ac47e6138f05cb0950486704eafd66eae75eec4
Cr-Commit-Position: refs/heads/master@{#27573}