Extract 'computeLineStarts' utility.

pkg/analyzer/lib/src/task/html.dart

Index: pkg/analyzer/lib/src/task/html.dart
diff --git a/pkg/analyzer/lib/src/task/html.dart b/pkg/analyzer/lib/src/task/html.dart
index b603f1f7139c2dc6c96f6cc5abfa232b86155334..219e1ee6e482320acd08651cfe9ba65d77e74ead 100644
--- a/pkg/analyzer/lib/src/task/html.dart
+++ b/pkg/analyzer/lib/src/task/html.dart
@@ -360,12 +360,7 @@ class ParseHtmlTask extends SourceBasedAnalysisTask {
    * Compute [LineInfo] for the given [content].
    */
   static LineInfo _computeLineInfo(String content) {
-    List<int> lineStarts = <int>[0];
-    for (int index = 0; index < content.length; index++) {
-      if (content.codeUnitAt(index) == 0x0A) {
-        lineStarts.add(index + 1);
-      }
-    }
+    List<int> lineStarts = StringUtilities.computeLineStarts(content);
     return new LineInfo(lineStarts);
   }
 }