[AF] Add flag to enable custom font weight for primary info

The goal is to allow experimentation with different font weights
for primary info for Payment Methods and Addresses suggestions on
the Autofill dropdown.

Screenshots on Windows (Googlers only): https://drive.google.com/open?id=1BhZdvN0l9GTzZv2kvim7_OCE9r9OsOhK

Bug: 882525
Change-Id: I9d1ec9ad662e858bd0d9c85c3b31849f13220b86
Reviewed-on: https://chromium-review.googlesource.com/1217171
Commit-Queue: Fabio Tirelo <[email protected]>
Reviewed-by: Vasilii Sukhanov <[email protected]>
Reviewed-by: Sebastien Seguin-Gagnon <[email protected]>
Cr-Commit-Position: refs/heads/master@{#590316}
diff --git a/chrome/browser/flag_descriptions.h b/chrome/browser/flag_descriptions.h
index baa2ebe5..2eb91b7 100644
--- a/chrome/browser/flag_descriptions.h
+++ b/chrome/browser/flag_descriptions.h
@@ -1673,6 +1673,9 @@
 extern const char kAutofillDropdownLayoutName[];
 extern const char kAutofillDropdownLayoutDescription[];
 
+extern const char kAutofillPrimaryInfoStyleExperimentName[];
+extern const char kAutofillPrimaryInfoStyleExperimentDescription[];
+
 extern const char kDoodlesOnLocalNtpName[];
 extern const char kDoodlesOnLocalNtpDescription[];