Make newLinePositions array.

Runtime/ui/txt/linebreaker.cs

 
         static LineBreaker _instance;
 
-        public static List<int> newLinePositions {
-            get {
-                if (_newLinePositions == null)
-                    _newLinePositions = new List<int>();
-                return _newLinePositions;
+        public static int[] newLinePositions(string text, out int count) {
+            count = 0;
+            for (var i = 0; i < text.Length; i++) {
+                if (text[i] == '\n') {
+                    count++;
+                }
+            }
+
+            count++;
+
+            if (_newLinePositions == null || _newLinePositions.Length < count) {
+                _newLinePositions = new int[count];
+            }
+
+            count = 0;
+            for (var i = 0; i < text.Length; i++) {
+                if (text[i] == '\n') {
+                    _newLinePositions[count++] = i;
+                }
+            _newLinePositions[count++] = text.Length;
+
+            return _newLinePositions;
-        static List<int> _newLinePositions;
+        static int[] _newLinePositions;
 
         TextBuff _textBuf;
         float[] _charWidths;

Runtime/ui/txt/paragraph.cs

                 ? this._paragraphStyle.maxLines ?? 1
                 : this._paragraphStyle.maxLines ?? 0;
 
-            var newLinePositions = LineBreaker.newLinePositions;
-            this._computeNewLinePositions(newLinePositions);
+            var newLinePositions = LineBreaker.newLinePositions(this._text, out int newLineCount);
-            for (var newlineIndex = 0; newlineIndex < newLinePositions.Count; ++newlineIndex) {
+            for (var newlineIndex = 0; newlineIndex < newLineCount; ++newlineIndex) {
                 if (lineLimit != 0 && this._lineRanges.Count >= lineLimit) {
                     break;
                 }
                     lineEndExcludingWhitespace, lineEndIncludingNewline, hardBreak));
                 this._lineWidths.Add(widths[i]);
             }
-        }
-
-        void _computeNewLinePositions(List<int> newLinePositions) {
-            newLinePositions.Clear();
-            for (var i = 0; i < this._text.Length; i++) {
-                if (this._text[i] == '\n') {
-                    newLinePositions.Add(i);
-                }
-            }
-
-            newLinePositions.Add(this._text.Length);
         }
 
         int _computeMaxWordCount() {