MRUCacheBase - Added Swap method to exchange contents of two MRUCache

base/containers/mru_cache.h

Index: base/containers/mru_cache.h
diff --git a/base/containers/mru_cache.h b/base/containers/mru_cache.h
index ed1ad251a2f607ee0b2a8f0384d9368474f4cf54..4bacf68cb58cf40f7a44fb5a94e978896a8ec383 100644
--- a/base/containers/mru_cache.h
+++ b/base/containers/mru_cache.h
@@ -16,6 +16,7 @@
 #ifndef BASE_CONTAINERS_MRU_CACHE_H_
 #define BASE_CONTAINERS_MRU_CACHE_H_
 
+#include <algorithm>
 #include <list>
 #include <map>
 #include <utility>
@@ -137,6 +138,14 @@ class MRUCacheBase {
     return index_iter->second;
   }
 
+  // Exchanges the contents of |this| by the contents of the |other|.
+  void Swap(MRUCacheBase& other) {
+    ordering_.swap(other.ordering_);
+    index_.swap(other.index_);
+    std::swap(deletor_, other.deletor_);
+    std::swap(max_size_, other.max_size_);
+  }
+
   // Erases the item referenced by the given iterator. An iterator to the item
   // following it will be returned. The iterator must be valid.
   iterator Erase(iterator pos) {