Purge new localstorage memory cache when under memory pressure.

content/browser/dom_storage/local_storage_context_mojo.h

Index: content/browser/dom_storage/local_storage_context_mojo.h
diff --git a/content/browser/dom_storage/local_storage_context_mojo.h b/content/browser/dom_storage/local_storage_context_mojo.h
index 90997500fe50007dcf2c67adcc836d368601806a..62257b85163f035c8168bfdc339457a9178f9d44 100644
--- a/content/browser/dom_storage/local_storage_context_mojo.h
+++ b/content/browser/dom_storage/local_storage_context_mojo.h
@@ -45,6 +45,10 @@ class CONTENT_EXPORT LocalStorageContextMojo {
   void DeleteStorageForPhysicalOrigin(const url::Origin& origin);
   void Flush();
 
+  // Clears any caches, to free up as much memory as possible. Next access to
+  // storage for a particular origin will reload the data from the database.
+  void PurgeMemory();
+
   leveldb::mojom::LevelDBDatabaseAssociatedRequest DatabaseRequestForTesting();
 
  private: