diff --git a/buffet/states/state_change_queue.cc b/buffet/states/state_change_queue.cc
new file mode 100644
index 0000000..a288c0f
--- /dev/null
+++ b/buffet/states/state_change_queue.cc
@@ -0,0 +1,42 @@
+// Copyright 2014 The Chromium OS 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 <base/logging.h>
+
+#include "buffet/states/state_change_queue.h"
+
+namespace buffet {
+
+StateChangeQueue::StateChangeQueue(size_t max_queue_size)
+    : max_queue_size_(max_queue_size) {
+  CHECK_GT(max_queue_size_, 0) << "Max queue size must not be zero";
+}
+
+bool StateChangeQueue::NotifyPropertiesUpdated(const StateChange& change) {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  state_changes_.push_back(change);
+  while (state_changes_.size() > max_queue_size_) {
+    // Queue is full.
+    // Merge the two oldest records into one. The merge strategy is:
+    //  - Move non-existent properties from element [old] to [new].
+    //  - If both [old] and [new] specify the same property,
+    //    keep the value of [new].
+    //  - Keep the timestamp of [new].
+    auto element_old = state_changes_.begin();
+    auto element_new = std::next(element_old);
+    // This will skip elements that exist in both [old] and [new].
+    element_new->property_set.insert(element_old->property_set.begin(),
+                                     element_old->property_set.end());
+    state_changes_.erase(element_old);
+  }
+  return true;
+}
+
+std::vector<StateChange> StateChangeQueue::GetAndClearRecordedStateChanges() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  // Return the accumulated state changes and clear the current queue.
+  return std::move(state_changes_);
+}
+
+}  // namespace buffet