Adds the ability to skip includes.

Adds the ability to skip includes.

Checks for a flag set in the toplevel dictionary of a file, and if its set, the includes for this file will be skipped. In the Chrome build, this allows us to write final .gyp files with all flags preprocessed and to not modify anything based on common.gypi.

This reverts r1723 (write link deps file) since this new GN integration replaces it.

BUG=307571

[brettw, 2013-10-15 17:03:00]

The GN-side change is https://codereview.chromium.org/26561005/

[Nico, 2013-10-15 17:12:50]

https://codereview.chromium.org/27353003/diff/1/pylib/gyp/input.py
File pylib/gyp/input.py (right):

https://codereview.chromium.org/27353003/diff/1/pylib/gyp/input.py#newcode233
pylib/gyp/input.py:233: not build_file_data['skip_includes']):
This maybe doesn't have to be so general. Your generated gyp files won't have
'include' sections, the only thing you care about is that build/gyp_chromium
adds a -Ibuild/common.gypi which you don't want for gyp files written by gn.

Where will gn write its gyp files to? Probably somewhere in its output
directory? How will higher-up gyp files depend on a gn-written gyp file? How
will these generated gyp files be converted to ninja files?

Maybe build/gyp_chromium could detect if it's processing gn-generated ninja
files and not add the -I switch in that case (which would require that they are
processed in a second pass, independent of the regular gyp files, but that's
maybe what's going to happen anyhow.)

[brettw, 2013-10-15 17:20:02]

https://codereview.chromium.org/27353003/diff/1/pylib/gyp/input.py
File pylib/gyp/input.py (right):

https://codereview.chromium.org/27353003/diff/1/pylib/gyp/input.py#newcode233
pylib/gyp/input.py:233: not build_file_data['skip_includes']):
GYP files that depend on this would just name the GYP file. There is nothing
special. Currently the GYP files are just written to the source tree. I will
likely add a new directory, but that would mean we need to update the GYP files
to reference that new directory.

There isn't a second pass for GN-generated ones. Everything is generated at once
which allows libraries and settings to flow through the dependency tree like
normal.

[Nico, 2013-10-15 18:20:59]

lgtm