ElementVisibilityObserver: use ExecutionContext's document.

third_party/WebKit/Source/core/dom/ElementVisibilityObserverTest.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/ElementVisibilityObserver.h"
+
+#include "core/dom/DOMImplementation.h"
+#include "core/dom/Document.h"
+#include "core/html/HTMLDivElement.h"
+#include "core/html/HTMLDocument.h"
+#include "core/testing/DummyPageHolder.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace blink {
+
+namespace {
+
+class ElementVisibilityObserverTest : public ::testing::Test {
+ protected:
+  void SetUp() override { m_dummyPageHolder = DummyPageHolder::create(); }
+
+  Document& document() { return m_dummyPageHolder->document(); }
+
+ private:
+  std::unique_ptr<DummyPageHolder> m_dummyPageHolder;
+};
+
+TEST_F(ElementVisibilityObserverTest, ObserveElementWithoutDocumentFrame) {
+  HTMLElement* element = HTMLDivElement::create(
+      *DOMImplementation::create(document())->createHTMLDocument("test"));
+  ElementVisibilityObserver* observer =
+      new ElementVisibilityObserver(element, nullptr);
+  observer->start();
+  observer->stop();
+  // It should not crash.
+}
+
+}  // anonymous namespace
+
+}  // blink namespace