Port and test more assists.

pkg/analysis_services/lib/src/correction/source_range.dart

Index: pkg/analysis_services/lib/src/correction/source_range.dart
diff --git a/pkg/analysis_services/lib/src/correction/source_range.dart b/pkg/analysis_services/lib/src/correction/source_range.dart
index a0c3a46c5eedc42aab3b2f6159d12d8b973c9b23..f0bc18c10855aefb6c83c2ee2e2ef45f54b07d09 100644
--- a/pkg/analysis_services/lib/src/correction/source_range.dart
+++ b/pkg/analysis_services/lib/src/correction/source_range.dart
@@ -24,9 +24,14 @@ SourceRange rangeEndEnd(a, b) {
   return new SourceRange(offset, length);
 }
 
+SourceRange rangeEndLength(a, int length) {
+  int offset = a is int ? a : a.end;
+  return new SourceRange(offset, length);
+}
+
 SourceRange rangeEndStart(a, b) {
   int offset = a.end;
-  var length = b.offset - offset;
+  var length = (b is int ? b : b.offset) - offset;
   return new SourceRange(offset, length);
 }