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..84373f39d08278ba0bf11a483ed8810806377ed7 100644
--- a/third_party/protobuf/proto_library.gni
+++ b/third_party/protobuf/proto_library.gni
@@ -63,6 +63,12 @@
 #       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 proto_in_dir.
+#       WARNING: This options should not be used in Chrome code until
+#       http://crbug.com/691451 is resolved.
+#
 # Parameters for compiling the generated code:
 #
 #   component_build_force_source_set (Default=false)
@@ -277,6 +283,12 @@ template("proto_library") {
       }
     }
 
+    if (defined(invoker.import_dirs)) {
+      foreach(path, invoker.import_dirs) {
+        args += ["--import-dir=" + rebase_path(path, root_build_dir)]
+      }
+    }
+
     # System protoc is not used so it's necessary to build a chromium one.
     inputs = [
       protoc_path,