Implement an API to allow passing an "ap" parameter to component updates.

components/update_client/utils.h

Index: components/update_client/utils.h
diff --git a/components/update_client/utils.h b/components/update_client/utils.h
index af353f76d67634f33c7aac80d9d7c0bf357c574d..eed5bb054e9b334b23ae0c930f8066b4d8161ea4 100644
--- a/components/update_client/utils.h
+++ b/components/update_client/utils.h
@@ -99,6 +99,9 @@ bool VerifyFileHash256(const base::FilePath& filepath,
 // Returns true if the |brand| parameter matches ^([a-zA-Z]{4})?$ .
 bool IsValidBrand(const std::string& brand);
 
+// Returns true if the |ap| parameter matches ^[-+_=a-zA-Z0-9]{0,256}$ .
+bool IsValidAp(const std::string& ap);
+
 // Removes the unsecure urls in the |urls| parameter.
 void RemoveUnsecureUrls(std::vector<GURL>* urls);