Fix the check for client hints count

The number of client hints requested by origin can be as high as
blink::mojom::WebClientHintsType::kLast + 1.

Bug: 735518
Change-Id: I6b5f2552b1f55f01e9b9aff33ce1ff33af8f125c
Reviewed-on: https://chromium-review.googlesource.com/961539Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Tarun Bansal <tbansal@chromium.org>
Cr-Commit-Position: refs/heads/master@{#542967}

chrome/browser/client_hints/client_hints_observer.cc

@@ -42,9 +42,13 @@ void ClientHintsObserver::PersistClientHints(
   if (!primary_url.is_valid() || !content::IsOriginSecure(primary_url))
     return;
 
+  DCHECK(!client_hints.empty());
+  DCHECK_LE(client_hints.size(),
+            static_cast<size_t>(blink::mojom::WebClientHintsType::kLast) + 1);
+
   if (client_hints.empty() ||
       client_hints.size() >
-          static_cast<int>(blink::mojom::WebClientHintsType::kLast)) {
+          (static_cast<size_t>(blink::mojom::WebClientHintsType::kLast) + 1)) {
     // Return early if the list does not have the right number of values.
     // Persisting wrong number of values to the disk may cause errors when
     // reading them back in the future.