Fix PaintLayer::compositingContainer for self-painting non-stacked layers

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 e0fd7c42fcc8036eb677214af75f1d7c28b67929..1d2b509a5e3e9325646956edda46a6b652b70810 100644
--- a/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
+++ b/third_party/WebKit/Source/core/paint/PaintLayerTest.cpp
@@ -663,6 +663,24 @@ TEST_P(PaintLayerTest, CompositingContainerFloatingIframe) {
   }
 }
 
+TEST_P(PaintLayerTest, CompositingContainerSelfPaintingNonStackedFloat) {
+  setBodyInnerHTML(
+      "<div id='container' style='position: relative'>"
+      "  <span id='span' style='opacity: 0.9'>"
+      "    <div id='target' style='columns: 1; float: left'></div>"

[chrishtr, 2017/02/08 16:56:20]

Add a comment that this is testing a non-stacked, self-painting
layer.

[Xianzhu, 2017/02/09 01:21:55]

Done.

+      "  </span>"
+      "</div>");
+
+  PaintLayer* target =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("target"))->layer();
+  PaintLayer* container =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("container"))->layer();
+  PaintLayer* span =
+      toLayoutBoxModelObject(getLayoutObjectByElementId("span"))->layer();
+  EXPECT_EQ(container, target->containingLayer());
+  EXPECT_EQ(span, target->compositingContainer());
+}
+
 TEST_P(PaintLayerTest, ColumnSpanLayerUnderExtraLayerScrolled) {
   setBodyInnerHTML(
       "<div id='columns' style='overflow: hidden; width: 80px; height: 80px; "