Fix to give `LineInfo` to options error spans.

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

Index: pkg/analyzer/lib/src/task/options.dart
diff --git a/pkg/analyzer/lib/src/task/options.dart b/pkg/analyzer/lib/src/task/options.dart
index 80ac44f714593cafc19bd5acfeb3558165b3b79b..9f22f7f647aec59ebd23f567d3067a99073e2c09 100644
--- a/pkg/analyzer/lib/src/task/options.dart
+++ b/pkg/analyzer/lib/src/task/options.dart
@@ -48,7 +48,7 @@ class GenerateOptionsErrorsTask extends SourceBasedAnalysisTask {
       'GenerateOptionsErrorsTask',
       createTask,
       buildInputs,
-      <ResultDescriptor>[ANALYSIS_OPTIONS_ERRORS]);
+      <ResultDescriptor>[ANALYSIS_OPTIONS_ERRORS, LINE_INFO]);
 
   final AnalysisOptionsProvider optionsProvider = new AnalysisOptionsProvider();
 
@@ -81,6 +81,7 @@ class GenerateOptionsErrorsTask extends SourceBasedAnalysisTask {
     // Record outputs.
     //
     outputs[ANALYSIS_OPTIONS_ERRORS] = errors;
+    outputs[LINE_INFO] = _computeLineInfo(content);
   }
 
   List<AnalysisError> _validate(Map<String, YamlNode> options) =>
@@ -96,6 +97,17 @@ class GenerateOptionsErrorsTask extends SourceBasedAnalysisTask {
   static GenerateOptionsErrorsTask createTask(
           AnalysisContext context, AnalysisTarget target) =>
       new GenerateOptionsErrorsTask(context, target);
+
+  /// 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) {

[Brian Wilkerson, 2015/10/27 13:18:29]

For Dart files we accept either CR, CR/LF, or LF as an end of line marker. I
think we need to do the same thing here.

[pquitslund, 2015/10/27 15:31:44]

I was folllowing HTML's suit but this is not a bad idea.

I'm probably being thick but could you point me to where line info is computed
for Dart files?

[Brian Wilkerson, 2015/10/27 15:59:44]

We compute line info while scanning, as part of the Scanner.

+        lineStarts.add(index + 1);
+      }
+    }
+    return new LineInfo(lineStarts);
+  }
 }
 
 /// Validates `linter` top-level options.