Hook up content/browser compile in GN build.

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.
 #
 # The 'proto_in_dir' variable is the path to the directory containing the
 # .proto files. If left out, it defaults to '.'.
 #
 # The 'proto_out_dir' variable specifies the path suffix that output files are
@@ skipping 103 matching lines @@
     }
 
     sources = get_target_outputs(":$action_name")
 
     direct_dependent_configs = [ "//third_party/protobuf:using_proto" ]
 
     deps = [
       ":$action_name",
       "//third_party/protobuf:protobuf_lite",
     ]
+
+    # The generated headers reference headers within protobuf_lite, so
+    # dependencies must be able to find those headers too.
+    forward_dependent_configs_from = [ "//third_party/protobuf:protobuf_lite" ]
   }
 }