Use correct clip container when computing acl for scroll children

third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp

Index: third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp
diff --git a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp
index 9c66cce9f35c2b09266c36f3e64035549ee6ec1b..b59b40ca10e6d5727876cf8ab6d540c41e6e68df 100644
--- a/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp
+++ b/third_party/WebKit/Source/core/layout/compositing/CompositedLayerMappingTest.cpp
@@ -626,4 +626,18 @@ TEST_F(CompositedLayerMappingTest, ScrollingContentsAndForegroundLayerPaintingPh
     EXPECT_FALSE(mapping->foregroundLayer());
 }
 
+TEST_F(CompositedLayerMappingTest, OverflowAndClippingWithACL)
+{
+    document().frame()->settings()->setPreferCompositingToLCDTextEnabled(true);
+    setBodyInnerHTML(
+        "<div style='height:700px; overflow-y:scroll; background-color:red;'>"
+        "  <div style='overflow:hidden; width: 700px; height:2000px;'>"
+        "    <div id='hidden' style='background-color:blue; width: 700px; height:2000px; position:relative;'></div>"
+        "  </div>"
+        "</div>");
+    CompositedLayerMapping* mapping = toLayoutBlock(getLayoutObjectByElementId("hidden"))->layer()->compositedLayerMapping();
+    ASSERT_TRUE(mapping->ancestorClippingLayer());
+    EXPECT_EQ(2000.f, mapping->ancestorClippingLayer()->size().height());
+}
+
 } // namespace blink