Precache manifest should not be added to fetcher pool which is full

components/precache/core/precache_fetcher.h

Index: components/precache/core/precache_fetcher.h
diff --git a/components/precache/core/precache_fetcher.h b/components/precache/core/precache_fetcher.h
index 324ab08fa474c727cafd5a9c55bd2ebe3a5955ce..77c04855873a713c9878df8f8456908125207260 100644
--- a/components/precache/core/precache_fetcher.h
+++ b/components/precache/core/precache_fetcher.h
@@ -101,6 +101,9 @@ class PrecacheFetcher {
   void Start();
 
  private:
+  friend class PrecacheFetcherTest;
+  FRIEND_TEST_ALL_PREFIXES(PrecacheFetcherTest, FetcherPoolMaxLimitReached);
+
   // Fetches the next resource or manifest URL, if any remain. Fetching is done
   // sequentially and depth-first: all resources are fetched for a manifest
   // before the next manifest is fetched. This is done to limit the length of