Add ContextLifecycleObserver::frame()

third_party/WebKit/Source/core/dom/ContextLifecycleObserver.cpp

+// 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 "core/dom/ContextLifecycleObserver.h"
+
+#include "core/dom/Document.h"
+#include "core/frame/LocalFrame.h"
+
+namespace blink {
+
+LocalFrame* ContextLifecycleObserver::frame() const {
+  return getExecutionContext() && getExecutionContext()->isDocument()
+             ? toDocument(getExecutionContext())->frame()
+             : nullptr;
+}
+}