Hook up content/browser compile in GN build.

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 7719567e8fb7e5cdd7c36281afdd2ef950409746..b35d2f3cc0998bb6cecfb1e7efaa6947cee44bd8 100644
--- a/third_party/protobuf/proto_library.gni
+++ b/third_party/protobuf/proto_library.gni
@@ -121,5 +121,9 @@ template("proto_library") {
       ":$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" ]
   }
 }