Changes the DEPS file to pull down the Dart VM source.

Changes the DEPS file to pull down the Dart VM source.

This pulls in the most recent dev-channel release of the
Dart source. It includes the Dart Editor, but it is planned
that this will be removed in the near future, which will
reduce checkout size.

The Dart source is under src/dart/dart. The disadvantage is
that this looks a bit silly, but it means that we don't have
to create/maintain yagr (Yet Another Git Repo).

From here, I'll work on translating the Dart gyp files over
to GN.

BUG=
R=jamesr@chromium.org

Committed: https://chromium.googlesource.com/external/mojo/+/309b11cd63c74285c17c883bd57792d831551ad7

[zra, 2014-10-30 16:52:47]

zra@google.com changed reviewers:
+ abarth@chromium.org

[zra, 2014-10-30 16:52:47]

Apologies that this does not match the results of our discussion yesterday, but
it is what I could manage after feedback from folks on my team.

[abarth-chromium, 2014-10-30 17:16:39]

If we pull in the Dart repo in this way, we'll add 800 MB to the Mojo checkout. 
For reference, the entire Mojo checkout currently (including all dependencies
from DEPS) is only 1.3G.

Of the 800 MB, only 208 MB is actually used currently (the rest is history). 
Based on our discussion, the part we actually need is dart/runtime and dart/pkg,
which is only about 50 MB.

In summary, I don't think this is a reasonable way of pulling Dart into Mojo. 
To make this landable, we'll need to:

1) Use the copy of zlib in //third_party/lib.
2) Remove the other third-party dependencies by disabling dart:io.
3) Reduce the size of the checkout to something more reasonable.

Ideally, we'd also remove the //dart/dart stutter, but fixing that is not a
requirement at this stage.

https://codereview.chromium.org/670263008/diff/1/DEPS
File DEPS (right):

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode95
DEPS:95: Var('chromium_git') + '/external/dart.git' + '@' +
Var('dart_revision'),
//dart/dart is a bit goofy.  Do we have a plan to fix that?

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode101
DEPS:101: Var('chromium_git') + '/chromium/src/third_party/sqlite.git' + '@' +
Var('sqlite_revision'),
Why does DartVM require sqlite and nss?  That doesn't make much sense.  Can we
cut this dependency before introducing it into the Mojo repo?  We don't
otherwise depend on sqlite and I don't think we want to start.

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode104
DEPS:104: Var('chromium_git') + '/chromium/src/third_party/zlib.git' + '@' +
Var('zlib_revision'),
We already have a copy of zlib in //third_party/zlib.  We shouldn't need to pull
in another one.

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode107
DEPS:107: Var('chromium_git') + '/chromium/src/net/third_party/nss.git' + '@' +
Var('net_nss_revision'),
It's pretty nutty to have two copies of nss.  From studying the Dart GYP files,
it looks like all these dependencies are to support the dart:io package.  In the
Mojo setting, we don't want to expose dart:io.  Instead, Dart programs should
use Mojo service to perform IO.  For example, instead of having direct access to
the file system via |File|, Dart programmings running inside Mojo should use the
Mojo storage service.

According to the docs, dart:io already doesn't work inside the browser.  Can we
build the DartVM with dart_io_support set to 0?  Then we won't need to pull in
these dependencies.

[zra, 2014-10-30 17:43:47]

How do you recommend reducing the size of the history?

https://codereview.chromium.org/670263008/diff/1/DEPS
File DEPS (right):

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode95
DEPS:95: Var('chromium_git') + '/external/dart.git' + '@' +
Var('dart_revision'),
On 2014/10/30 17:16:39, abarth wrote:
> //dart/dart is a bit goofy.  Do we have a plan to fix that?

The stutter, and I believe the history size issue, can be fixed now if checkout
from svn is possible. Otherwise, I'm afraid a strong argument for changing the
directory structure, or creating new repos, on our end would be needed. Since
that is a decision that would affect our whole team, I'll CC Ivan in case he
wants to comment.

https://codereview.chromium.org/670263008/diff/1/DEPS#newcode101
DEPS:101: Var('chromium_git') + '/chromium/src/third_party/sqlite.git' + '@' +
Var('sqlite_revision'),
On 2014/10/30 17:16:38, abarth wrote:
> Why does DartVM require sqlite and nss?  That doesn't make much sense.  Can we
> cut this dependency before introducing it into the Mojo repo?  We don't
> otherwise depend on sqlite and I don't think we want to start.

nss, zlib, and sqlite are for the dart:io secure socket library. If dart:io is
not needed, then neither are these. It is possible to build an embedding without
dart:io, so I have removed these dependencies.

[abarth-chromium, 2014-10-31 01:51:11]

This looks great except for the size issue.

On 2014/10/30 at 17:43:47, zra wrote:
> How do you recommend reducing the size of the history?

There are a couple of approaches we can take:

1) The simplest is to create a new git repo on googlesource.com and push a flat
copy of whatever parts of dart.git are appropriate for Mojo to consume. 
Presumably these would also be the parts that other embedders of DartVM would
want, so it might make sense to think about this repo as a source distribution
of DartVM for embedders.  Mojo could also consume a source distribution tarball
of DartVM from Google Storage or similar if that's easier, but my guess is git
is probably the distribution protocol of least resistance.

2) Another approach, which is perhaps easier to maintain, is to group all the
files needed for a source distribution of DartVM into a single directory in
dart.git.  We can then have googlesource.com automatically mirror that directory
as a separate git repo.  For example,
https://chromium.googlesource.com/chromium/blink-public/ is a similar mirror of
the "public" directory from Blink for consumers of Blink that require only the
headers.

I'd recommend (1), but either would be fine and there might be other solutions
as well.

[abarth-chromium, 2014-11-04 23:20:52]

I discussed this topic with jamesr and beng, and it might make sense to start
the bindings code from https://codereview.chromium.org/674383002/ in parallel
with solving these DEPS issues.  Ideally we'd like to be able to build and test
the Dart bindings continuously as we work on Mojo, but it's fine if we start out
in a state where there's bindings code in the repo that we can't yet build and
test.

[abarth-chromium, 2014-11-04 23:21:28]

On 2014/11/04 at 23:20:52, abarth wrote:
> ... make sense to start the bindings code ...
                        ^^^ landing

[zra, 2014-11-04 23:53:39]

On 2014/11/04 23:21:28, abarth wrote:
> On 2014/11/04 at 23:20:52, abarth wrote:
> > ... make sense to start the bindings code ...
>                         ^^^ landing

Yah, we can do that. To use the other CL, you just need the Dart SDK installed
with the dart binary on your path, so there's a pretty low barrier to using
what's there.

[jamesr, 2014-11-04 23:57:12]

jamesr@chromium.org changed reviewers:
+ jamesr@chromium.org

[jamesr, 2014-11-04 23:57:13]

Cool - can you add a README somewhere describing the process like this one:
https://github.com/domokit/mojo/blob/1a2084a2f46271a3b07f6e060d269314cbfd4405...
describing how someone interested in working in this area would go about it? 
Then as we improve this process over time we can slim down the README
instructions and they'll serve as a useful list of things that are still
difficult.

[zra, 2014-11-08 00:36:22]

zra@google.com changed reviewers:
+ beng@google.com

[zra, 2014-11-08 00:36:23]

Hopefully I have not misunderstood the conclusion of our meeting on Thursday.
I've moved the Dart stuff to a separate DEPS.dart file, and included
instructions in the Dart README on how to get the checkout.

The Dart revision pinned in DEPS.dart does not yet have the BUILD.gn files, but
those are written and under review here:

https://codereview.chromium.org/690923003/

I'll update this CL with the appropriate revision number once those are in.
Thoughts?

[abarth-chromium, 2014-11-08 01:12:17]

On 2014/11/08 at 00:36:23, zra wrote:
> I'll update this CL with the appropriate revision number once those are in.
Thoughts?

Oh, interesting.  I guess you can't just set something in the .gclient file
because OS is special-cased for deps_os?  /me defers to jamesr...

[zra, 2014-11-12 00:01:48]

The BUILD.gn files are landed in the Dart tree, and I've updated the Dart
version in DEPS.dart to one with the files. PTAL.

[jamesr, 2014-11-12 00:04:50]

Another way to handle this case is to add a second entry to the 'solutions' list
in the DEPS file that pulls in additional files. We could teach the fetch recipe
to have a parameter that adds this automatically for dart folks.  The way I've
seen this done is there is another 'solutions' entry that maps a folder that's a
peer to src/ and then the DEPS file in that peer maps in additional folders into
src/....  I think that way is marginally cleaner than munging the 'src' solution
entry.

[jamesr, 2014-11-12 00:04:50]

Another way to handle this case is to add a second entry to the 'solutions' list
in the DEPS file that pulls in additional files. We could teach the fetch recipe
to have a parameter that adds this automatically for dart folks.  The way I've
seen this done is there is another 'solutions' entry that maps a folder that's a
peer to src/ and then the DEPS file in that peer maps in additional folders into
src/....  I think that way is marginally cleaner than munging the 'src' solution
entry.

[jamesr, 2014-11-12 00:24:02]

I think this lgtm.  If you wanna go with the separate solution option we can do
that, but I don't think it's necessary for the first version.

[zra, 2014-11-12 15:13:55]

On 2014/11/12 00:24:02, jamesr wrote:
> I think this lgtm.  If you wanna go with the separate solution option we can
do
> that, but I don't think it's necessary for the first version.

Thanks. I like your suggestion. I'll commit this and work on changing over to
that.

[zra, 2014-11-12 15:14:09]

The CQ bit was checked by zra@google.com

[commit-bot: I haz the power, 2014-11-12 15:14:37]

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

[commit-bot: I haz the power, 2014-11-12 15:14:38]

Commit queue rejected this change because it did not recognize the base URL.
Please commit your change manually.

[zra, 2014-11-12 15:20:18]

On 2014/11/12 15:14:38, I haz the power (commit-bot) wrote:
> Commit queue rejected this change because it did not recognize the base URL.
> Please commit your change manually.

Sorry. New to git. I guess I have to be a member of the project on github to
commit?

[zra, 2014-11-12 16:08:00]

Committed patchset #7 (id:120001) manually as
309b11cd63c74285c17c883bd57792d831551ad7 (presubmit successful).