Refactor PaintLayer location and offset calculation especially for floats

third_party/WebKit/Source/core/paint/PaintLayerTest.cpp

Index: third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
diff --git a/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp b/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
index 3efb930a86ea17a6c9440608cd518bccf4f3e17d..59f4aec0704a2b8fb9b43a292dbcda7cf03a5137 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
@@ -550,8 +550,11 @@ TEST_P(PaintLayerTest, FloatLayerAndAbsoluteUnderInlineLayer) {
       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());
@@ -582,6 +585,7 @@ TEST_P(PaintLayerTest, FloatLayerUnderBlockUnderInlineLayer) {
       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());