Add an assert_no_deps variable to GN.

Add an assert_no_deps variable to GN.

This asserts that there is no dependency path to a given target.

BUG=

Committed: https://crrev.com/81aa4e8f010454835da6caa14507bcee73578e83
Cr-Commit-Position: refs/heads/master@{#371539}

[brettw, 2016-01-24 00:22:54]

The CQ bit was checked by brettw@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-01-24 00:23:00]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1621053002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1621053002/1

[brettw, 2016-01-24 00:24:31]

brettw@chromium.org changed reviewers:
+ dpranke@google.com

[brettw, 2016-01-24 00:24:32]

Had this patch partially done for several months. Last week somebody
accidentally started compiling Skia into NaCl stuff and the only reason they
noticed is that Skia doesn't compile in NaCl. I thought I should probably finish
this so we can add a few checks to prevent this kind of thing.

[commit-bot: I haz the power, 2016-01-24 01:08:26]

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

[commit-bot: I haz the power, 2016-01-24 01:08:27]

Dry run: This issue passed the CQ dry run.

[tfarina, 2016-01-24 11:50:19]

https://codereview.chromium.org/1621053002/diff/1/tools/gn/variables.h
File tools/gn/variables.h (right):

https://codereview.chromium.org/1621053002/diff/1/tools/gn/variables.h#newcode92
tools/gn/variables.h:92: extern const char kAssertNoDeps_Help[];
Looks like there is a mix of:

const char* kFoo_Help;

and

const char kFoo_Help[];

https://codereview.chromium.org/1621053002/diff/1/tools/gn/variables.h#newcode96
tools/gn/variables.h:96: extern const char* kCflags_Help;
Does this needs to be a pointer to char? Same for the following 4 XXX_Help
below.

[brettw, 2016-01-24 22:29:51]

In my testing if this feature I added some obvious checks which promptly failed.
Turns out content/common depends on blink! (The browser process shouldn't use
Blink.) I tracked down the blame for this stupidity and it was me. I think we
really need this assertion code...

[Dirk Pranke, 2016-01-26 01:17:39]

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

[Dirk Pranke, 2016-01-26 01:17:40]

lgtm

https://codereview.chromium.org/1621053002/diff/1/tools/gn/target_unittest.cc
File tools/gn/target_unittest.cc (right):

https://codereview.chromium.org/1621053002/diff/1/tools/gn/target_unittest.cc...
tools/gn/target_unittest.cc:691: // C depends in B and disallows depending on A.
This should fail.
nit: "depends on"

[brettw, 2016-01-26 17:42:00]

Comment fix

[brettw, 2016-01-26 17:42:03]

The CQ bit was checked by brettw@chromium.org

[brettw, 2016-01-26 17:42:04]

The patchset sent to the CQ was uploaded after l-g-t-m from dpranke@chromium.org
Link to the patchset: https://codereview.chromium.org/1621053002/#ps20001
(title: "Comment fix")

[commit-bot: I haz the power, 2016-01-26 17:43:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1621053002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1621053002/20001

[commit-bot: I haz the power, 2016-01-26 18:11:37]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2016-01-26 18:13:22]

Description was changed from

==========
Add an assert_no_deps variable to GN.

This asserts that there is no dependency path to a given target.

BUG=
==========

to

==========
Add an assert_no_deps variable to GN.

This asserts that there is no dependency path to a given target.

BUG=

Committed: https://crrev.com/81aa4e8f010454835da6caa14507bcee73578e83
Cr-Commit-Position: refs/heads/master@{#371539}
==========

[commit-bot: I haz the power, 2016-01-26 18:13:23]

Patchset 2 (id:??) landed as
https://crrev.com/81aa4e8f010454835da6caa14507bcee73578e83
Cr-Commit-Position: refs/heads/master@{#371539}