Mark when we may have been invalidated to early out on repaintTreeAfterLayout.

Source/core/rendering/RenderFlexibleBox.cpp

 /*
  * Copyright (C) 2011 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 215 matching lines @@
 
 void RenderFlexibleBox::layoutBlock(bool relayoutChildren)
 {
     ASSERT(needsLayout());
 
     if (!relayoutChildren && simplifiedLayout())
         return;
 
     LayoutRepainter repainter(*this, checkForRepaintDuringLayout());
 
+    setMayNeedInvalidation(true);
+
     if (updateLogicalWidthAndColumnWidth())
         relayoutChildren = true;
 
     LayoutUnit previousHeight = logicalHeight();
     setLogicalHeight(borderAndPaddingLogicalHeight() + scrollbarLogicalHeight());
 
     {
         LayoutStateMaintainer statePusher(*this, locationOffset());
 
         m_numberOfInFlowChildrenOnFirstLine = -1;
@@ skipping 857 matching lines @@
     size_t seenInFlowPositionedChildren = 0;
     bool shouldFlipMainAxis = !isColumnFlow() && !isLeftToRightFlow();
     for (size_t i = 0; i < children.size(); ++i) {
         RenderBox* child = children[i];
 
         if (child->isOutOfFlowPositioned()) {
             prepareChildForPositionedLayout(child, mainAxisOffset, crossAxisOffset, FlipForRowReverse);
             continue;
         }
 
+        child->setMayNeedInvalidation(true);
+
         LayoutUnit childPreferredSize = childSizes[i] + mainAxisBorderAndPaddingExtentForChild(child);
         setLogicalOverrideSize(child, childPreferredSize);
         if (childPreferredSize != mainAxisExtentForChild(child)) {
             child->setChildNeedsLayout(MarkOnlyThis);
         } else {
             // To avoid double applying margin changes in updateAutoMarginsInCrossAxis, we reset the margins here.
             resetAutoMarginsAndLogicalTopInCrossAxis(child);
         }
         // We may have already forced relayout for orthogonal flowing children in preferredMainAxisContentExtentForChild.
         bool forceChildRelayout = relayoutChildren && !childPreferredMainAxisContentExtentRequiresLayout(child, hasInfiniteLineLength);
@@ skipping 285 matching lines @@
             ASSERT(child);
             LayoutUnit lineCrossAxisExtent = lineContexts[lineNumber].crossAxisExtent;
             LayoutUnit originalOffset = lineContexts[lineNumber].crossAxisOffset - crossAxisStartEdge;
             LayoutUnit newOffset = contentExtent - originalOffset - lineCrossAxisExtent;
             adjustAlignmentForChild(child, newOffset - originalOffset);
         }
     }
 }
 
 }