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

components/precache/core/precache_fetcher.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
 #define COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_
 
 #include <stdint.h>
 
 #include <algorithm>
@@ skipping 106 matching lines @@
   // Starts fetching resources to precache. URLs are fetched sequentially. Can
   // be called from any thread. Start should only be called once on a
   // PrecacheFetcher instance.
   void Start();
 
   // Stops all precaching work. The PreacheFetcher should not be used after
   // calling this method.
   std::unique_ptr<PrecacheUnfinishedWork> CancelPrecaching();
 
  private:
+  friend class PrecacheFetcherTest;
+  FRIEND_TEST_ALL_PREFIXES(PrecacheFetcherTest, FetcherPoolMaxLimitReached);
+
   // Notifies the precache delete that precaching is done, and report
   // completion statistics.
   void NotifyDone(size_t remaining_manifest_urls_to_fetch,
                   size_t remaining_resource_urls_to_fetch);
 
   // 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
   // the |resource_urls_to_fetch_| list, reducing the memory usage.
   void StartNextFetch();
@@ skipping 108 matching lines @@
   std::unique_ptr<net::URLFetcher> network_url_fetcher_;
   int64_t response_bytes_;
   int64_t network_response_bytes_;
 
   DISALLOW_COPY_AND_ASSIGN(Fetcher);
 };
 
 }  // namespace precache
 
 #endif  // COMPONENTS_PRECACHE_CORE_PRECACHE_FETCHER_H_