[layoutng] Propagate fixed descendants of abs.

third_party/WebKit/Source/core/layout/ng/ng_out_of_flow_layout_part_test.cc

+// Copyright 2017 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/layout/ng/ng_out_of_flow_layout_part.h"
+
+#include "core/layout/LayoutTestHelper.h"
+#include "core/layout/ng/layout_ng_block_flow.h"
+
+namespace blink {
+namespace {
+
+class NGOutOfFlowLayoutPartTest : public RenderingTest {
+ public:
+  NGOutOfFlowLayoutPartTest() {
+    RuntimeEnabledFeatures::setLayoutNGEnabled(true);
+  };
+  ~NGOutOfFlowLayoutPartTest() {
+    RuntimeEnabledFeatures::setLayoutNGEnabled(false);
+  };
+};
+
+// Fixed blocks inside absolute blocks trigger otherwise unused while loop
+// inside NGOutOfFlowLayoutPart::Run.
+// This test exercises this loop by placing two fixed elements inside abs.
+TEST_F(NGOutOfFlowLayoutPartTest, FixedInsideAbs) {
+  setBodyInnerHTML(
+      R"HTML(
+      <style>
+        body{ padding:0px; margin:0px}
+        #rel { position:relative }
+        #abs {
+          position: absolute;
+          top:49px;
+          left:0px;
+        }
+        #pad {
+          width:100px;
+          height:50px;
+        }
+        #fixed1 {
+          position:fixed;
+          width:50px;
+        }
+        #fixed2 {
+          position:fixed;
+          top:9px;
+          left:7px;
+        }
+      </style>
+      <div id='rel'>
+        <div id='abs'>
+          <div id='pad'></div>
+          <div id='fixed1'>
+            <p>fixed static</p>
+          </div>
+          <div id='fixed2'>
+            <p>fixed plain</p>
+          </div>
+        </div>
+      </div>
+      )HTML");
+
+  // Test whether the oof fragments have been collected at NG->Legacy boundary.
+  Element* rel = document().getElementById("rel");
+  LayoutNGBlockFlow* block_flow = toLayoutNGBlockFlow(rel->layoutObject());
+  NGConstraintSpace* space =
+      NGConstraintSpace::CreateFromLayoutObject(*block_flow);
+  NGBlockNode node(block_flow);
+  RefPtr<NGPhysicalFragment> fragment = node.Layout(space);
+  EXPECT_EQ(fragment->OutOfFlowDescendants().size(), (size_t)2);
+
+  // Test the final result.
+  Element* fixed_1 = document().getElementById("fixed1");
+  Element* fixed_2 = document().getElementById("fixed2");
+  // fixed1 top is static: #abs.top + #pad.height
+  EXPECT_EQ(fixed_1->offsetTop(), LayoutUnit(99));
+  // fixed2 top is positioned: #fixed2.top
+  EXPECT_EQ(fixed_2->offsetTop(), LayoutUnit(9));
+};
+}
+}