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 d6c3fa416de693070e9605100bb8e6a027b4842f..a6b6c2dc6f64657f919fc04ba4973a6e79dcdb86 100644
--- a/components/precache/core/precache_fetcher.h
+++ b/components/precache/core/precache_fetcher.h
@@ -39,6 +39,10 @@ class PrecacheUnfinishedWork;
 // Visible for testing.
 extern const int kNoTracking;
 
+// Returns the maximum number of URLFetcher requests that can be on flight in
+// parallel.
+extern int GetDefaultMaxParallelFetches();
+
 // Public interface to code that fetches resources that the user is likely to
 // want to fetch in the future, putting them in the network stack disk cache.
 // Precaching is intended to be done when Chrome is not actively in use, likely
@@ -124,6 +128,8 @@ class PrecacheFetcher : public base::SupportsWeakPtr<PrecacheFetcher> {
   std::unique_ptr<PrecacheUnfinishedWork> CancelPrecaching();
 
  private:
+  friend class PrecacheFetcherTest;
+
   // Notifies the precache delete that precaching is done, and report
   // completion statistics.
   void NotifyDone(size_t remaining_manifest_urls_to_fetch,