Add Dart code to diff_view

pkg/compiler/lib/src/tokens/token.dart

Index: pkg/compiler/lib/src/tokens/token.dart
diff --git a/pkg/compiler/lib/src/tokens/token.dart b/pkg/compiler/lib/src/tokens/token.dart
index 4c33648e7d4ff715cd5c65990c1362d33f67988b..1b05a5fd88a9c50f4373e6bedfb6dbf7e0e844f1 100644
--- a/pkg/compiler/lib/src/tokens/token.dart
+++ b/pkg/compiler/lib/src/tokens/token.dart
@@ -112,6 +112,9 @@ abstract class Token implements Spannable {
     }
   }
 
+  /// The character offset of the end of this token within the source text.
+  int get charEnd => charOffset + charCount;
+
   int get hashCode => computeHashCode(charOffset, info, value);
 }