Return the enclosing composited PaintLayer rather than containingBlock 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 483 matching lines @@
   scroller->getScrollableArea()->setScrollOffset(ScrollOffset(0, 20),
                                                  ProgrammaticScroll);
   document().view()->updateAllLifecyclePhases();
   EXPECT_EQ(LayoutRect(0, 30, 50, 10), contentLayer->visualRect());
   EXPECT_EQ(LayoutRect(0, 30, 50, 5), content->visualRect());
 }
 
 TEST_P(PaintLayerTest, CompositingContainerFloat) {
   enableCompositing();
   setBodyInnerHTML(
-      "<div id='containingBlock' style='position: relative; z-index: 0'>"
-      "  <div style='backface-visibility: hidden'></div>"
-      "  <span style='clip-path: polygon(0px 15px, 0px 54px, 100px 0px)'>"
-      "    <div id='target' style='float: right; position: relative'></div>"
-      "  </span>"
+      "<div id='compositedContainer' style='position: relative;"
+      "    will-change: transform'>"
+      "  <div id='containingBlock' style='position: relative; z-index: 0'>"
+      "    <div style='backface-visibility: hidden'></div>"
+      "    <span style='clip-path: polygon(0px 15px, 0px 54px, 100px 0px)'>"
+      "      <div id='target' style='float: right; position: relative'></div>"
+      "    </span>"
+      "  </div>"
       "</div>");
 
   PaintLayer* target =
       toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
   PaintLayer* containingBlock =
       toLayoutBoxModelObject(getLayoutObjectByElementId("containingBlock"))
           ->layer();
   EXPECT_EQ(containingBlock, target->compositingContainer());
+  PaintLayer* compositedContainer =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("compositedContainer"))
+          ->layer();
+
+  // enclosingLayerWithCompositedLayerMapping is not needed or applicable to
+  // SPv2.
+  if (!RuntimeEnabledFeatures::slimmingPaintV2Enabled()) {
+    EXPECT_EQ(compositedContainer,
+              target->enclosingLayerWithCompositedLayerMapping(ExcludeSelf));
+  }
 }
 
 }  // namespace blink