[Mac/GN] Add a BUILD.gn file for //chrome/app_shim.

build/config/mac/rules.gni

Index: build/config/mac/rules.gni
diff --git a/build/config/mac/rules.gni b/build/config/mac/rules.gni
index 9aa1f92ae25f3c1b5dcd1129c26835cb37fd1feb..3c0bc86cc9aaf39d98e97722d4bc662fed356dc5 100644
--- a/build/config/mac/rules.gni
+++ b/build/config/mac/rules.gni
@@ -181,11 +181,15 @@ template("mac_app_bundle") {
                            "*",
                            [
                              "assert_no_deps",
+                             "configs",

[brettw, 2016/05/02 18:16:24]

This should be removed. It should actually give you an error (the docs for
forward_variables_from describes this) but I looked at the code and it doesn't
actually throw this error. I'll make a note to fix this.

The problem is that the executable has configs defined implicitly. This line
will clobber those defaults. Even if that wasn't the case, this line is
redundant with the code you wrote below to check the invoker configs.

[Robert Sesek, 2016/05/02 18:46:17]

Thanks. That was the open question, whether the clobber should happen or whether
we should do set addition.

                              "data_deps",
                              "info_plist",
                              "output_name",
                              "visibility",
                            ])
+    if (defined(invoker.configs)) {
+      configs += invoker.configs

[Dirk Pranke, 2016/04/28 21:20:45]

You don't need both line 184 and lines 190-192, I don't think, just add line
184. (And that should address your other concerns).

[Robert Sesek, 2016/04/28 21:34:54]

Hm, then you don't get the default configs that set things like the
include_dirs.

That's why I initially went with add_configs. If we let the executable override
the configs entirely, how would I add those default configs back in?

[Dirk Pranke, 2016/04/28 21:46:17]

Good question. I would've expected the configs to propagate, but I guess I'm not
sure what they'll do.

Brett, what's the right thing to do here?

[brettw, 2016/05/02 18:16:24]

These block is correct.

[Robert Sesek, 2016/05/02 18:46:17]

That didn't seem to work if I removed the clobber. GN complained:

ERROR at //chrome/app_shim/BUILD.gn:22:15: Duplicate item in list
  configs = [ "//build/config/compiler:wexit_time_destructors" ]
              ^-----------------------------------------------
See //chrome/app_shim/BUILD.gn:22:15: This was the previous definition.
  configs = [ "//build/config/compiler:wexit_time_destructors" ]
              ^-----------------------------------------------
See //chrome/app_shim/BUILD.gn:21:1: whence it was called.
mac_app_bundle("app_mode_loader") {
^----------------------------------
See //chrome/browser/BUILD.gn:440:7: which caused the file to be included.
      "//chrome/app_shim",
      ^------------------

But if I renamed it to invoker.extra_configs, then the error went away.

[brettw, 2016/05/02 19:18:01]

Don't know, I would recommend printing the various configs values.

Renaming it extra_configs is probably better though since these are additive and
not replaced. Just setting configs on an app bundle would imply to me that's the
full set of stuff getting set.

[Robert Sesek, 2016/05/02 21:01:19]

It's because the line I removed at 184 is actually in the
variables_to_not_forward_list, so configs was getting clobbered. We should
prevent that from happening, so I re-added configs to the exclude list and kept
extra_configs as the name.

+    }
     output_name = _output_name
     output_dir = "$target_out_dir/$_executable_target"
   }