Refactor PaintLayer location and offset calculation especially for floats

third_party/WebKit/Source/core/paint/PaintLayerTest.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/paint/PaintLayer.h"
 
 #include "core/html/HTMLIFrameElement.h"
 #include "core/layout/LayoutBoxModelObject.h"
 #include "core/layout/LayoutTestHelper.h"
 #include "core/layout/LayoutView.h"
@@ skipping 532 matching lines @@
   PaintLayer* floating =
       toLayoutBoxModelObject(getLayoutObjectByElementId("floating"))->layer();
   PaintLayer* absolute =
       toLayoutBoxModelObject(getLayoutObjectByElementId("absolute"))->layer();
   PaintLayer* span =
       toLayoutBoxModelObject(getLayoutObjectByElementId("span"))->layer();
   PaintLayer* container =
       toLayoutBoxModelObject(getLayoutObjectByElementId("container"))->layer();
 
   EXPECT_EQ(span, floating->parent());
+  EXPECT_EQ(container, floating->containingLayer());
   EXPECT_EQ(span, absolute->parent());
+  EXPECT_EQ(span, absolute->containingLayer());
   EXPECT_EQ(container, span->parent());
+  EXPECT_EQ(container, span->containingLayer());
 
   EXPECT_EQ(LayoutPoint(83, 83), floating->location());
   EXPECT_EQ(LayoutPoint(50, 50), absolute->location());
   EXPECT_EQ(LayoutPoint(133, 133), span->location());
   EXPECT_EQ(LayoutPoint(20, 20), container->location());
 
   EXPECT_EQ(LayoutPoint(-50, -50), floating->visualOffsetFromAncestor(span));
   EXPECT_EQ(LayoutPoint(50, 50), absolute->visualOffsetFromAncestor(span));
   EXPECT_EQ(LayoutPoint(83, 83), floating->visualOffsetFromAncestor(container));
   EXPECT_EQ(LayoutPoint(183, 183),
@@ skipping 10 matching lines @@
       "    </div>"
       "  </div>"
       "</span>");
 
   PaintLayer* floating =
       toLayoutBoxModelObject(getLayoutObjectByElementId("floating"))->layer();
   PaintLayer* span =
       toLayoutBoxModelObject(getLayoutObjectByElementId("span"))->layer();
 
   EXPECT_EQ(span, floating->parent());
+  EXPECT_EQ(span, floating->containingLayer());
 
   EXPECT_EQ(LayoutPoint(83, 83), floating->location());
   EXPECT_EQ(LayoutPoint(100, 100), span->location());
   EXPECT_EQ(LayoutPoint(83, 83), floating->visualOffsetFromAncestor(span));
   EXPECT_EQ(LayoutPoint(183, 183), floating->visualOffsetFromAncestor(
                                        document().layoutView()->layer()));
 }
 
 TEST_P(PaintLayerTest, CompositingContainerFloatingIframe) {
   enableCompositing();
@@ skipping 25 matching lines @@
 
   // enclosingLayerWithCompositedLayerMapping is not needed or applicable to
   // SPv2.
   if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
     EXPECT_EQ(compositedContainer,
               target->enclosingLayerWithCompositedLayerMapping(ExcludeSelf));
   }
 }
 
 }  // namespace blink