update_engine: Update libchrome APIs to r369476

The new libchrome has been ported from Chromium and some APIs have
changed. Make necessary changes at call sites.

Change-Id: I42e65bda7f1dbdf6f6e0ebf356d2cfea6b729193
diff --git a/update_manager/chromeos_policy.cc b/update_manager/chromeos_policy.cc
index 6ba6f82..e3d99d0 100644
--- a/update_manager/chromeos_policy.cc
+++ b/update_manager/chromeos_policy.cc
@@ -156,7 +156,9 @@
 
 // Checks whether |url| can be used under given download restrictions.
 bool IsUrlUsable(const string& url, bool http_allowed) {
-  return http_allowed || !base::StartsWithASCII(url, "http://", false);
+  return http_allowed ||
+         !base::StartsWith(url, "http://",
+                           base::CompareCase::INSENSITIVE_ASCII);
 }
 
 }  // namespace