Option added to protobuf build for import directories

third_party/protobuf/proto_library.gni

Index: third_party/protobuf/proto_library.gni
diff --git a/third_party/protobuf/proto_library.gni b/third_party/protobuf/proto_library.gni
index 7c74e4ef8e422b7ce8d29a5d668c2d44c46a23d7..1b32b9df9a069325149cc8d217d849d7fc41f006 100644
--- a/third_party/protobuf/proto_library.gni
+++ b/third_party/protobuf/proto_library.gni
@@ -63,6 +63,10 @@
 #       If adding protobuf library would be required, adds protobuf_full to deps
 #       instead of protobuf_lite.
 #
+#   import_dirs (optional)
+#       A list of extra import directories to be passed to protoc compiler. The
+#       default case is just the source directory.

[xyzzyz, 2017/01/20 18:27:40]

The "source directory" here is pretty ambiguous. I think what you mean (and what
you should put here instead) is proto_in_dir.

[Ramin Halavati, 2017/01/23 14:27:06]

Done.

+#
 # Parameters for compiling the generated code:
 #
 #   component_build_force_source_set (Default=false)
@@ -277,6 +281,11 @@ template("proto_library") {
       }
     }
 
+    if (defined(invoker.import_dirs)) {

[xyzzyz, 2017/01/20 18:27:40]

The comment and the name of the variable say it's a list of directories, but it
looks like it only supports a single directory.

[Ramin Halavati, 2017/01/23 14:27:06]

If one specifies several directories in import_dirs, rebase_path creates a list
of rebased paths and they are added to arguments with one single --import-dir
switch and protoc_wrapper accepts it this way.

+      args += ["--import-dir"]
+      args += rebase_path(invoker.import_dirs, proto_in_dir)

[xyzzyz, 2017/01/20 18:27:40]

Are you sure you want to rebase it on proto_in_dir? I think importing protos
that are in a subdirectory of proto_in_dir works already.

[Ramin Halavati, 2017/01/23 14:27:06]

I didn't find any documentations on this but it seems that all paths should be
specified relative to the directory of current BUILD.gn file. So I had to rebase
it to root_build_dir. I should note that this new change should also work for
directories which are not subdirectory of protos_in_dir.

+    }
+
     # System protoc is not used so it's necessary to build a chromium one.
     inputs = [
       protoc_path,