Factoring out camera_params.proto.

Change-Id: Idf886f9cb33764d505d5cff11ca766cea96d2024
diff --git a/tools/build_rules/protobuf.bzl b/tools/build_rules/protobuf.bzl
index c9bb9ef..f6a98b8 100644
--- a/tools/build_rules/protobuf.bzl
+++ b/tools/build_rules/protobuf.bzl
@@ -72,7 +72,7 @@
     name = '%s__proto_srcs' % name,
     srcs = [src],
     deps = [('%s__proto_srcs' % o_name) for o_name in deps],
-    visibility = ['//visibility:private'],
+    visibility = visibility,
   )
   basename = src[:-len('.proto')]
   native.cc_library(