Add Angle GN build file.

Add Angle GN build file.

BUG=
R=kbr@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=273684

[Ken Russell (switch to Gerrit), 2014-05-29 22:29:11]

+ANGLE team as FYI

LGTM

How will we be reminded to keep this up to date when ANGLE rolls? Is there a GN
bot?

I guess there's no possibility of using the enumerate_files.py script anymore to
autogenerate the file lists?

[brettw, 2014-05-30 00:16:55]

On 2014/05/29 22:29:11, Ken Russell wrote:
> +ANGLE team as FYI
> 
> LGTM
> 
> How will we be reminded to keep this up to date when ANGLE rolls? Is there a
GN
> bot?

Yes, there are Linux GN bots. No Windows yet.


> I guess there's no possibility of using the enumerate_files.py script anymore
to
> autogenerate the file lists?

We can run scripts but I don't think we should be doing that. It's slow to fork
and no other component does this.

[brettw, 2014-05-30 00:53:24]

Committed patchset #2 manually as r273684 (presubmit successful).

[Shannon Woods, 2014-05-30 15:51:28]

On 2014/05/30 00:53:24, brettw wrote:
> Committed patchset #2 manually as r273684 (presubmit successful).

Do we now need to update this file as well every time we roll? We've gone to
some pains to unify our build management so that we don't have to separately
maintain Visual Studio and gyp files, and to narrow the Chrome-ANGLE
interdependency to a single point, so if this can't be automatically generated,
that's a bit frustrating.

[Jamie Madill, 2014-05-30 16:01:52]

On 2014/05/30 15:51:28, Shannon Woods wrote:
> On 2014/05/30 00:53:24, brettw wrote:
> > Committed patchset #2 manually as r273684 (presubmit successful).
> 
> Do we now need to update this file as well every time we roll? We've gone to
> some pains to unify our build management so that we don't have to separately
> maintain Visual Studio and gyp files, and to narrow the Chrome-ANGLE
> interdependency to a single point, so if this can't be automatically
generated,
> that's a bit frustrating.

Could we possibly make it a part of the ANGLE source? That would have the
benefit of us
rolling in changes to the build with the corresponding ANGLE CL, instead of
updating all bundled changes when we roll.

[brettw, 2014-05-30 17:14:23]

On 2014/05/30 16:01:52, Jamie Madill wrote:
> On 2014/05/30 15:51:28, Shannon Woods wrote:
> > On 2014/05/30 00:53:24, brettw wrote:
> > > Committed patchset #2 manually as r273684 (presubmit successful).
> > 
> > Do we now need to update this file as well every time we roll? We've gone to
> > some pains to unify our build management so that we don't have to separately
> > maintain Visual Studio and gyp files, and to narrow the Chrome-ANGLE
> > interdependency to a single point, so if this can't be automatically
> generated,
> > that's a bit frustrating.
> 
> Could we possibly make it a part of the ANGLE source? That would have the
> benefit of us
> rolling in changes to the build with the corresponding ANGLE CL, instead of
> updating all bundled changes when we roll.

Yes! Basically each team should be maintaining their own build. I'm
bootstrapping a bunch of things because I'm blocked by it, but each team should
feel empowered to maintain their own build.

I don't think dynamically getting the file list from the disk is a good idea.
The Chrome build doesn't do this anywhere else, which means it's a bit
confusing, and it's slow to fork Python ~4 times each time you run GYP/GN.

Here's how I would do it if I were you:

You would put your lists of files in a single .gypi with different variables for
each type of file. Example:
http://src.chromium.org/viewvc/chrome/trunk/src/ppapi/ppapi_sources.gypi

You would include this file and reference these lists from your .gyp file(s) in
the sources section (you can see some .gyp files in the ppapi directory there
include that).

Move the BUILD.gn file to the angle repo in the root angle dir (this is so
Chrome code can refer to it as "//third_party/angle" rather than something like
"//third_party/angle/src:angle"). At the top you would read the .gypi values
like this file does:
http://src.chromium.org/viewvc/chrome/trunk/src/ppapi/BUILD.gn

And you can reference the .gypi variables from the BUILD.gn file so you only
have one place to maintain the sources. Note that the gypi_to_gn script doesn't
do conditions or anything, it just reads lists.