Unify UUID/GUID generation code across base and blink

chrome/browser/push_messaging/push_messaging_app_identifier.cc

Index: chrome/browser/push_messaging/push_messaging_app_identifier.cc
diff --git a/chrome/browser/push_messaging/push_messaging_app_identifier.cc b/chrome/browser/push_messaging/push_messaging_app_identifier.cc
index d4f7e7063188aadd5c5ab6cedf9ebfeba8b1cc0b..812f00bf8961dcd47428250ea620cf5ae0290fa1 100644
--- a/chrome/browser/push_messaging/push_messaging_app_identifier.cc
+++ b/chrome/browser/push_messaging/push_messaging_app_identifier.cc
@@ -66,7 +66,9 @@ void PushMessagingAppIdentifier::RegisterProfilePrefs(
 PushMessagingAppIdentifier PushMessagingAppIdentifier::Generate(
     const GURL& origin,
     int64_t service_worker_registration_id) {
-  std::string guid = base::GenerateGUID();
+  // Use uppercase GUID for consistency with GUIDs Push has already sent to GCM.
+  // Also allows detecting case mangling; see code commented "crbug.com/461867".
+  std::string guid = base::ToUpperASCII(base::GenerateGUID());
   CHECK(!guid.empty());
   std::string app_id =
       kPushMessagingAppIdentifierPrefix + origin.spec() + kSeparator + guid;