Add base::UnguessableToken

mojo/common/common_custom_types.typemap

Index: mojo/common/common_custom_types.typemap
diff --git a/mojo/common/common_custom_types.typemap b/mojo/common/common_custom_types.typemap
index 46ee53f7718c5b08b456e42c9873e8b5d6773f92..9cac985006f54b6093a672c7108ad1f67de213ad 100644
--- a/mojo/common/common_custom_types.typemap
+++ b/mojo/common/common_custom_types.typemap
@@ -5,6 +5,7 @@
 mojom = "//mojo/common/common_custom_types.mojom"
 public_headers = [
   "//base/files/file_path.h",
+  "//base/nonce.h",
   "//base/strings/string16.h",
   "//base/time/time.h",
   "//base/values.h",
@@ -25,6 +26,7 @@ type_mappings = [
   "mojo.common.mojom.FilePath=base::FilePath",
   "mojo.common.mojom.DictionaryValue=base::DictionaryValue",
   "mojo.common.mojom.ListValue=base::ListValue",
+  "mojo.common.mojom.Nonce=base::Nonce",

[dcheng, 2016/09/13 23:19:06]

If we expect people to pass Nonce by value (and it sounds like we do?), then
this should be annotated with [copyable_pass_by_value]

[tguilbert, 2016/09/14 22:40:47]

From danakj@'s comment earlier in the thread, I think the preferred way is via
const ref.

   "mojo.common.mojom.String16=base::string16",
   "mojo.common.mojom.Time=base::Time[copyable_pass_by_value]",
   "mojo.common.mojom.TimeDelta=base::TimeDelta[copyable_pass_by_value]",