Fix leaking animation in floating action button. (#3575)

examples/stocks/test/locale_test.dart

@@ -20,10 +20,6 @@ void main() {
       tester.setLocale("es", "US");
       tester.pump();
       expect(tester, hasWidget(find.text('MERCADO')));
-
-      // TODO(abarth): We're leaking an animation. We should track down the leak
-      // and plug it rather than waiting for the animation to end here.
-      tester.pump(const Duration(seconds: 1));
     });
   });
 }

packages/flutter/lib/src/material/floating_action_button.dart

@@ -109,6 +109,12 @@ class _FloatingActionButtonState extends State<FloatingActionButton> {
     ));
   }
 
+  @override
+  void dispose() {
+    _childSegueController.dispose();
+    super.dispose();
+  }
+
   @override
   void didUpdateConfig(FloatingActionButton oldConfig) {
     super.didUpdateConfig(oldConfig);

packages/flutter/lib/src/scheduler/binding.dart

@@ -250,10 +250,17 @@ abstract class SchedulerBinding extends BindingBase {
           exception: reason,
           library: 'scheduler library',
           informationCollector: (StringBuffer information) {
+            if (transientCallbackCount == 1) {
               information.writeln(
-              'There ${ transientCallbackCount == 1 ? "was one transient callback" : "were $transientCallbackCount transient callbacks" } '
-              'left. The stack traces for when they were registered are as follows:'
+                'There was one transient callback left. '
+                'The stack traces for when it was registered is as follows:'
               );
+            } else {
+              information.writeln(
+                'There were $transientCallbackCount transient callbacks left. '
+                'The stack traces for when they were registered are as follows:'
+              );
+            }
             for (int id in _transientCallbacks.keys) {
               _FrameCallbackEntry entry = _transientCallbacks[id];
               information.writeln('-- callback $id --');