Initial support for nested multicol layout.

Source/core/layout/MultiColumnFragmentainerGroup.h

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MultiColumnFragmentainerGroup_h
 #define MultiColumnFragmentainerGroup_h
 
 #include "core/layout/LayoutMultiColumnFlowThread.h"
 
 namespace blink {
@@ skipping 15 matching lines @@
 // need more columns than what a group has room for, we'll create another group and put them there
 // (and make them appear in the next outer fragmentainer).
 class MultiColumnFragmentainerGroup {
 public:
     MultiColumnFragmentainerGroup(LayoutMultiColumnSet&);
 
     bool isLastGroup() const;
 
     // Position within the LayoutMultiColumnSet.
     LayoutUnit logicalTop() const { return m_logicalTop; }
+    void setLogicalTop(LayoutUnit logicalTop) { m_logicalTop = logicalTop; }
 
     LayoutUnit logicalHeight() const { return m_columnHeight; }
 
     LayoutSize offsetFromColumnSet() const;
 
+    // Return the block offset from the enclosing flow thread, if nested. In the coordinate space
+    // of the enclosing flow thread.
+    LayoutUnit blockOffsetInEnclosingFlowThread() const;
+
     // The top of our flow thread portion
     LayoutUnit logicalTopInFlowThread() const { return m_logicalTopInFlowThread; }
     void setLogicalTopInFlowThread(LayoutUnit logicalTopInFlowThread) { m_logicalTopInFlowThread = logicalTopInFlowThread; }
 
     // The bottom of our flow thread portion
     LayoutUnit logicalBottomInFlowThread() const { return m_logicalBottomInFlowThread; }
     void setLogicalBottomInFlowThread(LayoutUnit logicalBottomInFlowThread) { ASSERT(logicalBottomInFlowThread >= m_logicalTopInFlowThread); m_logicalBottomInFlowThread = logicalBottomInFlowThread; }
 
     // The height of our flow thread portion
     LayoutUnit logicalHeightInFlowThread() const { return m_logicalBottomInFlowThread - m_logicalTopInFlowThread; }
@@ skipping 116 matching lines @@
     const MultiColumnFragmentainerGroup& last() const { return m_groups.last(); }
 
     typedef Vector<MultiColumnFragmentainerGroup, 1>::iterator iterator;
     typedef Vector<MultiColumnFragmentainerGroup, 1>::const_iterator const_iterator;
 
     iterator begin() { return m_groups.begin(); }
     const_iterator begin() const { return m_groups.begin(); }
     iterator end() { return m_groups.end(); }
     const_iterator end() const { return m_groups.end(); }
 
+    size_t size() const { return m_groups.size(); }
+    MultiColumnFragmentainerGroup& operator[](size_t i) { return m_groups.at(i); }
+    const MultiColumnFragmentainerGroup& operator[](size_t i) const { return m_groups.at(i); }
+
     void append(const MultiColumnFragmentainerGroup& group) { m_groups.append(group); }
-
     void shrink(size_t size) { m_groups.shrink(size); }
 
 private:
     LayoutMultiColumnSet& m_columnSet;
 
     Vector<MultiColumnFragmentainerGroup, 1> m_groups;
 };
 
 } // namespace blink
 
 #endif // MultiColumnFragmentainerGroup_h