Remove TimelineEnumerator/TimelineTreeEnumerator dead code (#9858)

Author: h3xds1nz

src/Microsoft.DotNet.Wpf/src/PresentationCore/System/Windows/Media/Animation/Subtree.cs

@@ -267,151 +267,4 @@ internal Clock Current
 
         #endregion // Data
     }
-
-    /// <summary>
-    /// An object that enumerates the timelines of a tree of Timeline
-    /// objects.
-    /// </summary>
-    internal struct TimelineTreeEnumerator
-    {
-        #region Constructor
-        /// <summary>
-        /// Creates an enumerator that iterates over a subtree of timelines
-        /// in prefix order.
-        /// </summary>
-        /// <param name="root">
-        /// The timeline that is the root of the subtree to enumerate.
-        /// </param>
-        /// <param name="processRoot">
-        /// True to include the root in the enumeration, false otherwise.
-        /// </param>
-        internal TimelineTreeEnumerator(Timeline root, bool processRoot)
-        {
-            _rootTimeline = root;
-            _flags = processRoot ? (SubtreeFlag.Reset | SubtreeFlag.ProcessRoot) : SubtreeFlag.Reset;
-
-            // Start with stacks of capacity 10. That's relatively small, yet
-            // it covers very large trees without reallocation of stack data.
-            // Note that given the way we use the stacks we need one less entry
-            // for indices than for timelines, as we don't care what the index
-            // of the root timeline is.
-            _indexStack = new Stack(9);
-            _timelineStack = new Stack<Timeline>(10);
-        }
-        #endregion // Constructor
-
-        #region Methods
-
-        /// <summary>
-        /// Causes the enumerator to not enumerate the timelines in the subtree rooted
-        /// at the current timeline.
-        /// </summary>
-        internal void SkipSubtree()
-        {
-            _flags |= SubtreeFlag.SkipSubtree;
-        }
-
-        /// <summary>
-        /// Advances the enumerator to the next element of the collection.
-        /// </summary>
-        /// <returns>
-        /// true if the enumerator was successfully advanced to the next element,
-        /// false if the enumerator has passed the end of the collection.
-        /// </returns>
-        public bool MoveNext()
-        {
-            TimelineCollection  children;
-
-            // Get the iteration started in the right place, if we are just starting
-            if ((_flags & SubtreeFlag.Reset) != 0)
-            {
-                // The reset flag takes effect only once
-                _flags &= ~SubtreeFlag.Reset;
-
-                // We are just getting started. The first timeline is the root
-                _timelineStack.Push(_rootTimeline);
-
-                // If we are not supposed to return the root, simply skip it
-                if ((_flags & SubtreeFlag.ProcessRoot) == 0)
-                {
-                    MoveNext();
-                }
-            }
-            else if (_timelineStack.Count > 0)
-            {
-                // Only TimelineGroup can have children
-                TimelineGroup timelineGroup = _timelineStack.Peek() as TimelineGroup;
-
-                // The next timeline is possibly the first child of the current timeline
-                // If we have children move to the first one, unless we were
-                // asked to skip the subtree
-                if (  ((_flags & SubtreeFlag.SkipSubtree) == 0) 
-                    && timelineGroup != null 
-                    && (children = timelineGroup.Children) != null
-                    && children.Count > 0
-                    )
-                {
-                    _timelineStack.Push(children[0]);
-                    _indexStack.Push((int)0);
-                }
-                else
-                {
-                    // The skip subtree flag takes effect only once
-                    _flags &= ~SubtreeFlag.SkipSubtree;
-
-                    // Move to the first ancestor that has unvisited children,
-                    // then move to the first unvisited child. If we get to
-                    // the root it means we are done.
-                    _timelineStack.Pop();
-                    while (_timelineStack.Count > 0)
-                    {
-                        timelineGroup = _timelineStack.Peek() as TimelineGroup;
-
-                        // This has to be non-null since we already went down the tree
-                        children = timelineGroup.Children;
-
-                        int index = (int)_indexStack.Pop() + 1;
-
-                        if (index < children.Count)
-                        {
-                            // Move to the next child, and we are done
-                            _timelineStack.Push(children[index]);
-                            _indexStack.Push(index);
-                            break;
-                        }
-
-                        _timelineStack.Pop();
-                    }
-                }
-            }
-
-            return _timelineStack.Count > 0;
-        }
-
-        #endregion // Methods
-
-        #region Properties
-
-        /// <summary>
-        /// Gets the current element in the collection.
-        /// </summary>
-        internal Timeline Current
-        {
-            get
-            {
-                return _timelineStack.Peek();
-            }
-        }
-
-        #endregion // Properties
-
-        #region Data
-
-        private Timeline            _rootTimeline;
-        private SubtreeFlag         _flags;
-        private Stack               _indexStack;
-        private Stack<Timeline>     _timelineStack;
-
-        #endregion // Data
-    }
 }