Fix analyzer warnings (#7523)

I see these errors in Atom on my Mac. I'm not sure why they're not being
picked up by the bots.

packages/flutter/lib/src/rendering/box.dart

@@ -936,7 +936,7 @@ class _IntrinsicDimensionsCacheEntry {
 /// these classes, however, you must implement the algorithm yourself.
 abstract class RenderBox extends RenderObject {
   @override
-  void setupParentData(RenderObject child) {
+  void setupParentData(@checked RenderObject child) {
     if (child.parentData is! BoxParentData)
       child.parentData = new BoxParentData();
   }
@@ -1823,7 +1823,7 @@ abstract class RenderBox extends RenderObject {
   /// ```
   // TODO(ianh): Fix the type of the argument here once https://github.com/dart-lang/sdk/issues/25232 is fixed
   @override
-  void handleEvent(PointerEvent event, HitTestEntry entry) {
+  void handleEvent(PointerEvent event, @checked HitTestEntry entry) {
     super.handleEvent(event, entry);
   }
 

packages/flutter/lib/src/widgets/basic.dart

@@ -2073,7 +2073,7 @@ class Flex extends MultiChildRenderObjectWidget {
   }
 
   @override
-  void updateRenderObject(BuildContext context, RenderFlex renderObject) {
+  void updateRenderObject(BuildContext context, @checked RenderFlex renderObject) {
     renderObject
       ..direction = direction
       ..mainAxisAlignment = mainAxisAlignment

packages/flutter/lib/src/widgets/framework.dart

@@ -3456,7 +3456,7 @@ abstract class RenderObjectElement extends BuildableElement {
   }
 
   @override
-  void update(RenderObjectWidget newWidget) {
+  void update(@checked RenderObjectWidget newWidget) {
     super.update(newWidget);
     assert(widget == newWidget);
     assert(() { _debugUpdateRenderObjectOwner(); return true; });

packages/flutter_driver/lib/src/driver.dart

@@ -285,7 +285,7 @@ class FlutterDriver {
     if (_printCommunication)
       _log.info(message);
     if (_logCommunicationToFile) {
-      f.File file = fs.file(p.join(testOutputsDirectory, 'flutter_driver_commands_${_driverId}.log'));
+      f.File file = fs.file(p.join(testOutputsDirectory, 'flutter_driver_commands_$_driverId.log'));
       file.createSync(recursive: true); // no-op if file exists
       file.writeAsStringSync('${new DateTime.now()} $message\n', mode: f.FileMode.APPEND, flush: true);
     }