Option added to protobuf build for import directories

third_party/protobuf/proto_library.gni

 # Copyright 2014 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
 # Compile a protocol buffer.
 #
 # Protobuf parameters:
 #
 #   proto_in_dir (optional)
 #       Specifies the path relative to the current BUILD.gn file where
@@ skipping 45 matching lines @@
 #   generator_plugin_options (optional)
 #       Extra flags passed to the plugin. See cc_generator_options.
 #
 #   deps (optional)
 #       Additional dependencies.
 #
 #   use_protobuf_full (optional)
 #       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)
 #       When set true the generated code will be compiled as a source set in
 #       the component build. This does not affect static builds.  If you are
 #       exporting symbols from a component, this is required to prevent those
 #       symbols from being stripped. If you're not using dllexports in
 #       cc_generator_options, it's usually best to leave this false.
 #
 #   defines (optional)
@@ skipping 194 matching lines @@
         rel_cc_out_dir,
       ]
       if (defined(invoker.generator_plugin_options)) {
         args += [
           "--plugin-options",
           invoker.generator_plugin_options,
         ]
       }
     }
 
+    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,
     ]
     deps = [
       protoc_label,
     ]
 
     if (generate_with_plugin) {
       inputs += [ plugin_path ]
@@ skipping 78 matching lines @@
       ":$action_name",
     ]
 
     # This will link any libraries in the deps (the use of invoker.deps in the
     # action won't link it).
     if (defined(invoker.deps)) {
       deps += invoker.deps
     }
   }
 }