Ability to return the height of fragmentainer groups that don't yet exist.

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 750 matching lines @@
     lineBox.setPaginationStrut(LayoutUnit());
     lineBox.setIsFirstAfterPageBreak(false);
     LayoutUnit pageLogicalHeight = pageLogicalHeightForOffset(logicalOffset);
     if (!pageLogicalHeight)
         return;
     LayoutUnit remainingLogicalHeight = pageRemainingLogicalHeightForOffset(logicalOffset, AssociateWithLatterPage);
     int lineIndex = lineCount(&lineBox);
     if (remainingLogicalHeight < lineHeight || (shouldBreakAtLineToAvoidWidow() && lineBreakToAvoidWidow() == lineIndex)) {
         LayoutUnit paginationStrut = calculatePaginationStrutToFitContent(logicalOffset, remainingLogicalHeight, lineHeight);
         LayoutUnit newLogicalOffset = logicalOffset + paginationStrut;
-        // The new offset may require us to insert a new row for columns (fragmentainer group).
-        // Give the multicol machinery an opportunity to do so (before checking the height of a
-        // column that wouldn't have existed yet otherwise).
-        paginatedContentWasLaidOut(newLogicalOffset + lineHeight);
         // Moving to a different page or column may mean that its height is different.
         pageLogicalHeight = pageLogicalHeightForOffset(newLogicalOffset);
         if (lineHeight > pageLogicalHeight) {
             // Too tall to fit in one page / column. Give up. Don't push to the next page / column.
             // TODO(mstensho): Get rid of this. This is just utter weirdness, but the other browsers
             // also do something slightly similar, although in much more specific cases than we do here,
             // and printing Google Docs depends on it.
+            paginatedContentWasLaidOut(logicalOffset + lineHeight);
             return;
         }
 
         // We need to insert a break now, either because there's no room for the line in the
         // current column / page, or because we have determined that we need a break to satisfy
         // widow requirements.
         if (shouldBreakAtLineToAvoidWidow() && lineBreakToAvoidWidow() == lineIndex) {
             clearShouldBreakAtLineToAvoidWidow();
             setDidBreakAtLineToAvoidWidow();
         }
         if (shouldSetStrutOnBlock(*this, lineBox, logicalOffset, lineIndex, pageLogicalHeight)) {
             // Note that when setting the strut on a block, it may be propagated to parent blocks
             // later on, if a block's logical top is flush with that of its parent. We don't want
             // content-less portions (struts) at the beginning of a block before a break, if it can
             // be avoided. After all, that's the reason for setting struts on blocks and not lines
             // in the first place.
             LayoutUnit strut = paginationStrut + logicalOffset + marginBeforeIfFloating();
             setPaginationStrutPropagatedFromChild(strut);
         } else {
             delta += paginationStrut;
             lineBox.setPaginationStrut(paginationStrut);
             lineBox.setIsFirstAfterPageBreak(true);
         }
+        paginatedContentWasLaidOut(newLogicalOffset + lineHeight);
         return;
     }
 
     if (remainingLogicalHeight == pageLogicalHeight) {
         // We're at the very top of a page or column.
         if (lineBox != firstRootBox())
             lineBox.setIsFirstAfterPageBreak(true);
         // If this is the first line in the block, and the block has a top border, padding, or (in
         // case it's a float) margin, we may want to set a strut on the block, so that everything
         // ends up in the next column or page. Setting a strut on the block is also important when
@@ skipping 2043 matching lines @@
     FrameView* frameView = document().view();
     LayoutUnit top = LayoutUnit((style()->position() == FixedPosition) ? 0 : frameView->scrollOffset().height());
     int visibleHeight = frameView->visibleContentRect(IncludeScrollbars).height();
     if (size().height() < visibleHeight)
         top += (visibleHeight - size().height()) / 2;
     setY(top);
     dialog->setCentered(top);
 }
 
 } // namespace blink