Add comment to api_packages property

Bug: N/A
Test: N/A
Change-Id: I38791170993484cdae26edee9595a74802853176
diff --git a/sysprop/sysprop_library.go b/sysprop/sysprop_library.go
index 643fe8e..6e8e306 100644
--- a/sysprop/sysprop_library.go
+++ b/sysprop/sysprop_library.go
@@ -38,7 +38,9 @@
 	// Determine who owns this sysprop library. Possible values are
 	// "Platform", "Vendor", or "Odm"
 	Property_owner string
-	Api_packages   []string
+
+	// list of package names that will be documented and publicized as API
+	Api_packages []string
 }
 
 type commonProperties struct {