Introduce RenderingTest::getLayoutObjectByElementId().

third_party/WebKit/Source/core/layout/LayoutBoxTest.cpp

 // Copyright 2014 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/layout/LayoutBox.h"
 
 #include "core/html/HTMLElement.h"
 #include "core/layout/ImageQualityController.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace blink {
 
 class LayoutBoxTest : public RenderingTest {
 };
 
 TEST_F(LayoutBoxTest, BackgroundObscuredInRect)
 {
     setBodyInnerHTML("<style>.column { width: 295.4px; padding-left: 10.4px; } .white-background { background: red; position: relative; overflow: hidden; border-radius: 1px; }"
         ".black-background { height: 100px; background: black; color: white; } </style>"
         "<div class='column'> <div> <div id='target' class='white-background'> <div class='black-background'></div> </div> </div> </div>");
-    Element* element = document().getElementById("target");
-    ASSERT_TRUE(element);
-    ASSERT_TRUE(element->layoutObject());
-    ASSERT_TRUE(element->layoutObject()->boxDecorationBackgroundIsKnownToBeObscured());
+    LayoutObject* layoutObject = getLayoutObjectByElementId("target");
+    ASSERT_TRUE(layoutObject);
+    ASSERT_TRUE(layoutObject->boxDecorationBackgroundIsKnownToBeObscured());
 }
 
 } // namespace blink