GN configs for ipc fuzzer.

build/config/features.gni

Index: build/config/features.gni
diff --git a/build/config/features.gni b/build/config/features.gni
index 72a5b5e576a95ed86d134ca627f72d14c215ad0e..acf9a63a3b2a3457152e0e60f6f683663475a98a 100644
--- a/build/config/features.gni
+++ b/build/config/features.gni
@@ -116,6 +116,9 @@ declare_args() {
   # Enable printing with print preview. It does not imply
   # enable_basic_printing. It's possible to build Chrome with preview only.
   enable_print_preview = !is_android && !is_chromecast && !is_ios
+
+  # Don't build IPC fuzzer by default.

[Nico, 2016/04/22 21:17:53]

can you remind me again why this is off by default?

[Oliver Chang, 2016/04/22 21:30:32]

It changes some behaviour (based on the ENABLE_IPC_FUZZER define), and breaks
component builds.

That said, we do want to have a better way of preventing breakages for this
config. If possible we'd like to look into adding builders to the main waterfall
and CQ for this configuration.

+  enable_ipc_fuzzer = false

[Dirk Pranke, 2016/04/22 23:18:11]

In GN we don't want to add arguments globally if they're not needed globally
(i.e. if we don't need to check them all over the place).

It looks like the ENABLE_IPC_FUZZER define is only used in a few places, so
instead of adding it here, you should create a separate ipc_fuzzer.gni file that
declares this arg and a config that adds the define, and then only include that
.gni file from the files that need it (ipc and a couple of places that take
command line switches, I think)?

[Oliver Chang, 2016/04/25 18:16:06]

OK, done. I'm a little concerned about header files that use ENABLE_IPC_FUZZER
which are included by other targets. It seems to build, but should the the
configs += [ "..." ] in the various BUILD.gn files be public_configs instead (or
even all_dependent_configs)?

[Dirk Pranke, 2016/04/25 18:48:58]

If the defines are needed in public headers (i.e., headers which are included by
other components),
then you should use public_configs instead of configs.

It is rare to really need all_dependent_configs.

I don't know enough about the structure of the ipc #includes to know what the
right thing to do really is, but if that guidance isn't enough, let me know and
we can work through it together.

[Oliver Chang, 2016/04/25 19:25:50]

Thanks, I've changed ipc/BUILD.gn to use public_configs.

 }
 
 # Additional dependent variables -----------------------------------------------