Use Layout Opportunity Iterator to position new FC blocks.

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

Index: third_party/WebKit/Source/core/layout/ng/ng_floating_object.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_floating_object.h b/third_party/WebKit/Source/core/layout/ng/ng_floating_object.h
index 29d71d83cc0ec9b06f157d32f202176b73d6d765..29f9fd69fecbed97b686f72a7f8d2e865476364d 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_floating_object.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_floating_object.h
@@ -13,6 +13,7 @@
 #include "core/layout/ng/ng_physical_fragment.h"
 #include "core/style/ComputedStyle.h"
 #include "core/style/ComputedStyleConstants.h"
+#include "platform/wtf/Optional.h"
 #include "platform/wtf/RefPtr.h"
 
 namespace blink {
@@ -50,6 +51,10 @@ struct CORE_EXPORT NGFloatingObject : public RefCounted<NGFloatingObject> {
   NGLogicalOffset origin_offset;
   NGLogicalOffset from_offset;
 
+  // Calculated logical offset. It's never {@code nullopt} for a positioned
+  // float.
+  WTF::Optional<NGLogicalOffset> logical_offset;
+
   // Writing mode of the float's constraint space.
   NGWritingMode writing_mode;