Purge new localstorage memory cache when under memory pressure.

content/browser/dom_storage/local_storage_context_mojo.cc

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/dom_storage/local_storage_context_mojo.h"
 
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "components/leveldb/public/cpp/util.h"
@@ skipping 262 matching lines @@
 void LocalStorageContextMojo::Flush() {
   if (connection_state_ != CONNECTION_FINISHED) {
     RunWhenConnected(base::BindOnce(&LocalStorageContextMojo::Flush,
                                     weak_ptr_factory_.GetWeakPtr()));
     return;
   }
   for (const auto& it : level_db_wrappers_)
     it.second->level_db_wrapper()->ScheduleImmediateCommit();
 }
 
+void LocalStorageContextMojo::PurgeMemory() {
+  for (const auto& it : level_db_wrappers_)
+    it.second->level_db_wrapper()->PurgeMemory();
+}
+
 leveldb::mojom::LevelDBDatabaseAssociatedRequest
 LocalStorageContextMojo::DatabaseRequestForTesting() {
   DCHECK_EQ(connection_state_, NO_CONNECTION);
   connection_state_ = CONNECTION_IN_PROGRESS;
   leveldb::mojom::LevelDBDatabaseAssociatedRequest request =
       MakeRequestForTesting(&database_);
   OnDatabaseOpened(true, leveldb::mojom::DatabaseError::OK);
   return request;
 }
 
@@ skipping 291 matching lines @@
   for (const auto& info : usage) {
     url::Origin origin_candidate(info.origin);
     if (!origin_candidate.IsSameOriginWith(origin) &&
         origin_candidate.IsSamePhysicalOriginWith(origin))
       DeleteStorage(origin_candidate);
   }
   DeleteStorage(origin);
 }
 
 }  // namespace content