fix third_party_headers to work properly on Windows w/ ninja.

fix third_party_headers to work properly on Windows w/ ninja.

The setup_third_party.py script was hand-rolling an implementation of
os.path.relpath in order to be 2.5 compatible, and that was getting
confused when we had to generate forwarding headers from ninja's 
intermediate directory.

This patch reworks the python code to use relpath (since we require 2.6 now)
and work the same way regardless of platform or headers being generated, so
that we can have a single code path.

Full details in the bug.

R=tony@chromium.org
BUG=175273
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=182359

[Dirk Pranke, 2013-02-09 03:35:12]

PTAL ...

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
Let me know if you think this comment is too verbose. In addition, I waffled on
whether to add '<(DEPTH)' to include_dirs to ensure that this would always be
right, but I wasn't sure if we can safely assume that '<(DEPTH)' will always be
in the include_dirs path, or if gyp would be smart enough to remove duplicate
entries from include_dirs.

Thoughts?

[Ryan Sleevi, 2013-02-10 11:06:01]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
On 2013/02/09 03:35:12, Dirk Pranke wrote:
> Let me know if you think this comment is too verbose. In addition, I waffled
on
> whether to add '<(DEPTH)' to include_dirs to ensure that this would always be
> right, but I wasn't sure if we can safely assume that '<(DEPTH)' will always
be
> in the include_dirs path, 

GYP doesn't ensure this. You would have to manually specify it. I'm also not
sure how well that would work if you were trying to have it propagate to
dependencies (since the <(DEPTH) will be relative to the GYP file, as would
'..'). It may work via late expansion, though.

> or if gyp would be smart enough to remove duplicate
> entries from include_dirs.

It's supposed to - see
https://code.google.com/p/gyp/wiki/InputFormatReference#List_Singletons
> 
> Thoughts?

[tony, 2013-02-11 18:16:50]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
It sounds like we should have a direct_dependant_settings to add <(DEPTH) to
includes?

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.py (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.py:72: args: A list with 2 values, the input
dir and the output dir.
Nit: Can you update this docstring?

[Ryan Sleevi, 2013-02-11 18:19:17]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
On 2013/02/11 18:16:50, tony wrote:
> It sounds like we should have a direct_dependant_settings to add <(DEPTH) to
> includes?

<(DEPTH) won't be absolutized, so it would result in something like '-I../..',
which will work if you're in src/foo/bar/bar.gyp, but do nothing if you're in
src/baz/bat/frob/frob.gyp

That is, I don't think it'll do what you expect.

[tony, 2013-02-11 20:05:38]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
On 2013/02/11 18:19:18, Ryan Sleevi wrote:
> On 2013/02/11 18:16:50, tony wrote:
> > It sounds like we should have a direct_dependant_settings to add <(DEPTH) to
> > includes?
> 
> <(DEPTH) won't be absolutized, so it would result in something like '-I../..',
> which will work if you're in src/foo/bar/bar.gyp, but do nothing if you're in
> src/baz/bat/frob/frob.gyp
> 
> That is, I don't think it'll do what you expect.

I see.  It sounds like we should just hardcode '../..' which will be the 'src'
directory.

[Dirk Pranke, 2013-02-11 23:42:30]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
On 2013/02/11 18:19:18, Ryan Sleevi wrote:
> On 2013/02/11 18:16:50, tony wrote:
> > It sounds like we should have a direct_dependant_settings to add <(DEPTH) to
> > includes?
> 
> <(DEPTH) won't be absolutized, so it would result in something like '-I../..',
> which will work if you're in src/foo/bar/bar.gyp, but do nothing if you're in
> src/baz/bat/frob/frob.gyp
> 
> That is, I don't think it'll do what you expect.

Someone's confused. Maybe it's me :) Assuming we add this to include_dirs,
doesn't that get relativized as well as treated as a singleton? In otherwords, I
think it will / does?

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.py (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.py:72: args: A list with 2 values, the input
dir and the output dir.
On 2013/02/11 18:16:50, tony wrote:
> Nit: Can you update this docstring?

good catch. done.

[Ryan Sleevi, 2013-02-11 23:50:10]

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
File webkit/support/setup_third_party.gyp (right):

https://codereview.chromium.org/12224087/diff/3001/webkit/support/setup_third...
webkit/support/setup_third_party.gyp:25: # already (and always) be in the
include_dir path
On 2013/02/11 23:42:30, Dirk Pranke wrote:
> On 2013/02/11 18:19:18, Ryan Sleevi wrote:
> > On 2013/02/11 18:16:50, tony wrote:
> > > It sounds like we should have a direct_dependant_settings to add <(DEPTH)
to
> > > includes?
> > 
> > <(DEPTH) won't be absolutized, so it would result in something like
'-I../..',
> > which will work if you're in src/foo/bar/bar.gyp, but do nothing if you're
in
> > src/baz/bat/frob/frob.gyp
> > 
> > That is, I don't think it'll do what you expect.
> 
> Someone's confused. Maybe it's me :) Assuming we add this to include_dirs,
> doesn't that get relativized as well as treated as a singleton? In otherwords,
I
> think it will / does?

It's me. I'm the confused one. Ignore me.

[tony, 2013-02-12 00:08:30]

LGTM