Reporting: Cap number of reports in cache.

net/reporting/reporting_cache.h

Index: net/reporting/reporting_cache.h
diff --git a/net/reporting/reporting_cache.h b/net/reporting/reporting_cache.h
index 30ad0429e16d639f49b3cbd5ca61c66a67d14e70..122e0c81beaa662eaa44e0c9cc39297522b95311 100644
--- a/net/reporting/reporting_cache.h
+++ b/net/reporting/reporting_cache.h
@@ -159,6 +159,8 @@ class NET_EXPORT ReportingCache {
   }
 
  private:
+  const ReportingReport* FindReportToEvict() const;
+
   void MaybeAddWildcardClient(const ReportingClient* client);
 
   void MaybeRemoveWildcardClient(const ReportingClient* client);