Respect constrained height on nested multicol containers.

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

 /*
  * Copyright (C) 2012 Apple 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:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 609 matching lines @@
 }
 
 void LayoutMultiColumnFlowThread::appendNewFragmentainerGroupIfNeeded(
     LayoutUnit offsetInFlowThread,
     PageBoundaryRule pageBoundaryRule) {
   LayoutMultiColumnSet* columnSet =
       columnSetAtBlockOffset(offsetInFlowThread, pageBoundaryRule);
   if (!columnSet->newFragmentainerGroupsAllowed())
     return;
 
-  if (!columnSet->hasFragmentainerGroupForColumnAt(offsetInFlowThread,
-                                                   pageBoundaryRule)) {
-    FragmentationContext* enclosingFragmentationContext =
-        this->enclosingFragmentationContext();
-    // Not nested. We'll never need more rows than the one we already have then.
-    if (!enclosingFragmentationContext)
-      return;
-    ASSERT(!isLayoutPagedFlowThread());
+  if (columnSet->needsNewFragmentainerGroupAt(offsetInFlowThread,
+                                              pageBoundaryRule)) {
+    // We should never create additional fragmentainer groups unless we're in a
+    // nested fragmentation context.
+    DCHECK(enclosingFragmentationContext());
+
+    DCHECK(!isLayoutPagedFlowThread());
 
     // We have run out of columns here, so we need to add at least one more row
     // to hold more columns.
     LayoutMultiColumnFlowThread* enclosingFlowThread =
-        enclosingFragmentationContext->associatedFlowThread();
+        enclosingFragmentationContext()->associatedFlowThread();
     do {
       if (enclosingFlowThread) {
         // When we add a new row here, it implicitly means that we're inserting
         // another column in our enclosing multicol container. That in turn may
         // mean that we've run out of columns there too. Need to insert
         // additional rows in ancestral multicol containers before doing it in
         // the descendants, in order to get the height constraints right down
         // there.
         const MultiColumnFragmentainerGroup& lastRow =
             columnSet->lastFragmentainerGroup();
         // The top offset where where the new fragmentainer group will start in
         // this column set, converted to the coordinate space of the enclosing
         // multicol container.
         LayoutUnit logicalOffsetInOuter =
             lastRow.blockOffsetInEnclosingFragmentationContext() +
             lastRow.logicalHeight();
         enclosingFlowThread->appendNewFragmentainerGroupIfNeeded(
             logicalOffsetInOuter, AssociateWithLatterPage);
       }
 
       const MultiColumnFragmentainerGroup& newRow =
           columnSet->appendNewFragmentainerGroup();
       // Zero-height rows should really not occur here, but if it does anyway,
       // break, so that we don't get stuck in an infinite loop.
       ASSERT(newRow.logicalHeight() > 0);
       if (newRow.logicalHeight() <= 0)
         break;
-    } while (!columnSet->hasFragmentainerGroupForColumnAt(offsetInFlowThread,
-                                                          pageBoundaryRule));
+    } while (columnSet->needsNewFragmentainerGroupAt(offsetInFlowThread,
+                                                     pageBoundaryRule));
   }
 }
 
 bool LayoutMultiColumnFlowThread::isFragmentainerLogicalHeightKnown() {
   return isPageLogicalHeightKnown();
 }
 
 LayoutUnit LayoutMultiColumnFlowThread::fragmentainerLogicalHeightAt(
     LayoutUnit blockOffset) {
   return pageLogicalHeightForOffset(blockOffset);
@@ skipping 688 matching lines @@
     const {
   return MultiColumnLayoutState(m_lastSetWorkedOn);
 }
 
 void LayoutMultiColumnFlowThread::restoreMultiColumnLayoutState(
     const MultiColumnLayoutState& state) {
   m_lastSetWorkedOn = state.columnSet();
 }
 
 }  // namespace blink