Push the top margin of floats past all useless fragmentainers.

third_party/WebKit/Source/core/layout/LayoutBlockFlow.cpp

 /*
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 1021 matching lines @@
       // far only accounts for pushing the top border edge to the next
       // fragmentainer. We need to push the margin over as well, because
       // there's no break opportunity between margin and border.
       strut += marginBefore;
     } else {
       // Even if we didn't break before the border box to the next
       // fragmentainer, we need to check if we can fit the margin before it.
       if (pageLogicalHeightForOffset(logicalTopMarginEdge)) {
         LayoutUnit remainingSpace = pageRemainingLogicalHeightForOffset(
             logicalTopMarginEdge, AssociateWithLatterPage);
-        if (remainingSpace <= marginBefore)
-          strut += remainingSpace;
+        if (remainingSpace <= marginBefore) {
+          strut += calculatePaginationStrutToFitContent(
+              logicalTopMarginEdge, remainingSpace, marginBefore);
+        }
       }
     }
   }
   if (!strut) {
     // If we are unsplittable and don't fit, move to the next page or column
     // if that helps the situation.
     LayoutUnit newLogicalTopMarginEdge =
         adjustForUnsplittableChild(child, logicalTopMarginEdge);
     strut = newLogicalTopMarginEdge - logicalTopMarginEdge;
   }
@@ skipping 3551 matching lines @@
   return LayoutBlock::invalidatePaintIfNeeded(paintInvalidationState);
 }
 
 void LayoutBlockFlow::invalidateDisplayItemClients(
     PaintInvalidationReason invalidationReason) const {
   BlockFlowPaintInvalidator(*this).invalidateDisplayItemClients(
       invalidationReason);
 }
 
 }  // namespace blink