Make Dart_ScriptGetTokenInfo account for line_offset() and col_offset()

tools/coverage.dart

Index: tools/coverage.dart
diff --git a/tools/coverage.dart b/tools/coverage.dart
index 15333a6c9d7c50879cdb02dad013b4adb4610bfa..9958e4387830a034f30f180ffdbb0ab95e275af5 100644
--- a/tools/coverage.dart
+++ b/tools/coverage.dart
@@ -78,7 +78,7 @@ class Source {
 
   void SetLineInfo(List lineInfoTable) {
     // Each line is encoded as an array with first element being the line
-    // number, followed by pairs of (tokenPosition, textOffset).
+    // number, followed by pairs of (tokenPosition, columnNumber).
     lineInfoTable.forEach((List<int> line) {
       int lineNumber = line[0];
       for (int t = 1; t < line.length; t += 2) {