Replace uses of hash_map in //base

chromeos/system/statistics_provider.cc

Index: chromeos/system/statistics_provider.cc
diff --git a/chromeos/system/statistics_provider.cc b/chromeos/system/statistics_provider.cc
index c7144df5196d5af893341892cb124def354a3600..f42bc06fcc28a695922f9fe49d72187898ed959d 100644
--- a/chromeos/system/statistics_provider.cc
+++ b/chromeos/system/statistics_provider.cc
@@ -8,6 +8,7 @@
 
 #include "base/bind.h"
 #include "base/command_line.h"
+#include "base/containers/flat_map.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/json/json_file_value_serializer.h"
@@ -262,7 +263,7 @@ class StatisticsProviderImpl : public StatisticsProvider {
   bool oem_manifest_loaded_;
   std::string region_;
   std::unique_ptr<base::Value> regional_data_;
-  base::hash_map<std::string, RegionDataExtractor> regional_data_extractors_;
+  base::flat_map<std::string, RegionDataExtractor> regional_data_extractors_;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(StatisticsProviderImpl);