Animation API improvements (#21540)

diff --git a/dev/bots/analyze-sample-code.dart b/dev/bots/analyze-sample-code.dart
index 341e03e..e4e643a 100644
--- a/dev/bots/analyze-sample-code.dart
+++ b/dev/bots/analyze-sample-code.dart

@@ -267,7 +267,7 @@
           throw 'failed to parse error message (read line number as $lineNumber; total number of lines is ${lines.length}): $error';
         }
         final Line actualLine = lines[lineNumber - 1];
-        if (errorCode == 'unused_element') {
+        if (errorCode == 'unused_element' || errorCode == 'unused_local_variable') {
           // We don't really care if sample code isn't used!
         } else if (actualLine == null) {
           if (errorCode == 'missing_identifier' && lineNumber > 1 && buffer[lineNumber - 2].endsWith(',')) {
@@ -330,6 +330,9 @@
     sections.add(Section(line, 'Future<Null> expression$_expressionId() async { ', block.toList(), ' }'));
   } else if (block.first.startsWith('class ') || block.first.startsWith('enum ')) {
     sections.add(Section(line, null, block.toList(), null));
+  } else if ((block.first.startsWith('_') || block.first.startsWith('final ')) && block.first.contains(' = ')) {
+    _expressionId += 1;
+    sections.add(Section(line, 'void expression$_expressionId() { ', block.toList(), ' }'));
   } else {
     final List<String> buffer = <String>[];
     int subblocks = 0;