Add support for data deps.

Add support for data deps.

Data deps are non-linked dependencies of a target. They are built in parallel (they are not input dependencies). I redefined "data" to mean data file dependencies, and added a new "datadeps" contept for non-linked target dependencies.

Fix a bug to make it not crash if there's nothing to generate.

Add variable documentation for some vars.

Removed support for some builtin vars "root output dir name" and related. These had changed definition from when I originally wrote them, and I don't think there's any use for these values. We can add them back if we need.

I moved the variable name constant declarations from scope_per_file_provider to the new variables file which includes documentation.

I added support for getting the name of the current toolchain via a builtin variable.

I removed support for solink_module which is not necessary. This was a way to express a .dll target that isn't linked to its dependees, but that's no longer necessary for datadeps.



BUG=
R=scottmg@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=215976

[scottmg, 2013-08-06 20:27:58]

lgtm

https://codereview.chromium.org/22290010/diff/5001/tools/gn/command_desc.cc
File tools/gn/command_desc.cc (right):

https://codereview.chromium.org/22290010/diff/5001/tools/gn/command_desc.cc#n...
tools/gn/command_desc.cc:103: if (cmdline->HasSwitch(kIncludeDataDeps)) {
i feel like you probably always want to see these, at least as much as any other
dep

[brettw, 2013-08-06 21:10:22]

https://codereview.chromium.org/22290010/diff/5001/tools/gn/command_desc.cc
File tools/gn/command_desc.cc (right):

https://codereview.chromium.org/22290010/diff/5001/tools/gn/command_desc.cc#n...
tools/gn/command_desc.cc:103: if (cmdline->HasSwitch(kIncludeDataDeps)) {
Okay, I removed this and included them all the time.

[brettw, 2013-08-06 21:11:21]

Committed patchset #4 manually as r215976 (presubmit successful).