Add left_offset to NGFloatingObject and set it on legacy FloatingObject

third_party/WebKit/Source/core/layout/ng/ng_floating_object.h

 // 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.
 
 #ifndef NGFloatingObject_h
 #define NGFloatingObject_h
 
 #include "core/layout/ng/ng_block_node.h"
 #include "core/layout/ng/ng_constraint_space.h"
 #include "core/layout/ng/ng_units.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/ComputedStyleConstants.h"
 #include "platform/heap/Handle.h"
 
 namespace blink {
 
 class NGPhysicalFragment;
 
 // Struct that keeps all information needed to position floats in LayoutNG.
 struct CORE_EXPORT NGFloatingObject
     : public GarbageCollectedFinalized<NGFloatingObject> {

[ikilpatrick, 2017/02/10 01:53:41]

Also I assume we are performing copies of this object as it bubbles up?

[Gleb Lanbin, 2017/02/10 20:11:12]

yes, we're copying heap pointers 

   NGFloatingObject(NGPhysicalFragment* fragment,
                    NGConstraintSpace* space,
+                   const NGConstraintSpace* parent_space,
                    NGBlockNode* node,
                    const ComputedStyle& style,
                    const NGBoxStrut& margins)
-      : fragment(fragment), space(space), node(node), margins(margins) {
+      : fragment(fragment),
+        space(space),
+        parent_space(parent_space),
+        node(node),
+        margins(margins) {
     exclusion_type = NGExclusion::kFloatLeft;
     if (style.floating() == EFloat::kRight)
       exclusion_type = NGExclusion::kFloatRight;
     clear_type = style.clear();
   }
 
   RefPtr<NGPhysicalFragment> fragment;
   // TODO(glebl): Constraint space should be const here.
   Member<NGConstraintSpace> space;
+
+  // Parent space is used so we can calculate the inline offset relative to
+  // the genuine parent of this float.
+  Member<const NGConstraintSpace> parent_space;

[ikilpatrick, 2017/02/10 01:53:41]

This doesn't need to be stored here right?

[Gleb Lanbin, 2017/02/10 20:11:12]

we use the original parent's inline BFC offset in our calculation.

   Member<NGBlockNode> node;
   NGExclusion::Type exclusion_type;
   EClear clear_type;
   NGBoxStrut margins;
 
+  // In the case where a legacy FloatingObject is attached to not its own
+  // parent, e.g. a float surrounded by a bunch of nested empty divs,
+  // NG float fragment's LeftOffset() cannot be used as legacy FloatingObject's
+  // left offset because that offset should be relative to the genuine float
+  // parent.
+  // {@code left_offset} is calculated when we know to which parent this float
+  // would be attached.
+  LayoutUnit left_offset;
+
   DEFINE_INLINE_TRACE() {
     visitor->trace(space);
+    visitor->trace(parent_space);
     visitor->trace(node);
   }
 };
 
 }  // namespace blink
 
 #endif  // NGFloatingObject_h