Add more documentation for GN header checking

Add more documentation for GN header checking

Several people have been confused how the header checker works. This
significantly expands the documentation.

Committed: https://crrev.com/b24c0792cfe4babd048c7ba1d8031b4fd497a811
Cr-Commit-Position: refs/heads/master@{#382106}

[brettw, 2016-03-18 20:15:05]

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

[brettw, 2016-03-18 20:15:05]

https://codereview.chromium.org/1820493002/diff/1/tools/gn/variables.cc
File tools/gn/variables.cc (left):

https://codereview.chromium.org/1820493002/diff/1/tools/gn/variables.cc#oldco...
tools/gn/variables.cc:483: "Expansion of {{bundle_executable_dir}} in
create_bundle.";
This was on purpose, this line was 81 cols and wrapped funny.

[brettw, 2016-03-18 20:15:12]

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

[commit-bot: I haz the power, 2016-03-18 20:15:45]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1820493002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1820493002/1

[Dirk Pranke, 2016-03-18 21:02:25]

lgtm

[brettw, 2016-03-18 21:10:38]

The CQ bit was unchecked by brettw@chromium.org

[brettw, 2016-03-18 21:10:41]

The CQ bit was checked by brettw@chromium.org

[commit-bot: I haz the power, 2016-03-18 21:10:54]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1820493002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1820493002/1

[commit-bot: I haz the power, 2016-03-18 22:08:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-03-18 22:09:52]

Description was changed from

==========
Add more documentation for GN header checking

Several people have been confused how the header checker works. This
significantly expands the documentation.
==========

to

==========
Add more documentation for GN header checking

Several people have been confused how the header checker works. This
significantly expands the documentation.

Committed: https://crrev.com/b24c0792cfe4babd048c7ba1d8031b4fd497a811
Cr-Commit-Position: refs/heads/master@{#382106}
==========

[commit-bot: I haz the power, 2016-03-18 22:09:53]

Patchset 1 (id:??) landed as
https://crrev.com/b24c0792cfe4babd048c7ba1d8031b4fd497a811
Cr-Commit-Position: refs/heads/master@{#382106}