[layoutng] Better abspos support in legacy interop

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

 // 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/layout/ng/layout_ng_block_flow.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_fragment_base.h"
 #include "core/layout/LayoutAnalyzer.h"
 
 namespace blink {
@@ skipping 12 matching lines @@
 
   // TODO(layout-dev): This should be created in the constructor once instead.
   // There is some internal state which needs to be cleared between layout
   // passes (probably FirstChild(), etc).
   m_box = new NGBlockNode(this);
 
   NGFragmentBase* fragment;
   while (!m_box->Layout(constraint_space, &fragment))
     ;
 
+  if (isOutOfFlowPositioned()) {
+    // In legacy layout, abspos differs from regular blocks in that abspos
+    // blocks position themselves in their own layout, instead of getting
+    // positioned by their parent. So it we are a positioned block in a legacy-
+    // layout containing block, we have to emulate this positioning.
+    // Additionally, until we natively support abspos in LayoutNG, this code
+    // will also be reached though the layoutPositionedObjects call in
+    // NGBlockNode::CopyFragmentDataToLayoutBox.
+    LogicalExtentComputedValues computedValues;
+    computeLogicalWidth(computedValues);
+    setLogicalLeft(computedValues.m_position);
+    computeLogicalHeight(logicalHeight(), logicalTop(), computedValues);
+    setLogicalTop(computedValues.m_position);
+  }
+
   for (auto& descendant : fragment->PhysicalFragment()->OutOfFlowDescendants())
     descendant->UseOldOutOfFlowPositioning();
   clearNeedsLayout();
 }
 
 }  // namespace blink