Roll Observatory deps (charted -> ^0.3.0)

packages/usage/tool/grind.dart

Index: packages/usage/tool/grind.dart
diff --git a/packages/usage/tool/grind.dart b/packages/usage/tool/grind.dart
index da63dc2e34f4f7b274b7a8e56bf81f8629975ab4..f1d8121abe7a5b798bbb6bb6fff49d5b028c9880 100644
--- a/packages/usage/tool/grind.dart
+++ b/packages/usage/tool/grind.dart
@@ -8,40 +8,35 @@ import 'dart:io';
 
 import 'package:grinder/grinder.dart';
 
-final Directory BUILD_DIR = new Directory('build');
-final Directory BUILD_TEST_DIR = new Directory('build/test');
+final Directory _buildExampleDir = new Directory('build/example');
 
-void main(List<String> args) {
-  task('init', init);
-  task('build', build, ['init']);
-  task('clean', clean);
+main(List<String> args) => grind(args);
 
-  startGrinder(args);
-}
-
-/// Do any necessary build set up.
-void init(GrinderContext context) {
+@Task('Do any necessary build set up')
+void init() {
   // Verify we're running in the project root.
   if (!getDir('lib').existsSync() || !getFile('pubspec.yaml').existsSync()) {
     context.fail('This script must be run from the project root.');
   }
 
-  BUILD_TEST_DIR.createSync(recursive: true);
+  _buildExampleDir.createSync(recursive: true);
 }
 
-void build(GrinderContext context) {
+@Task()
+@Depends(init)
+void build() {
   // Compile `test/web_test.dart` to the `build/test` dir; measure its size.
-  File srcFile = new File('test/web_test.dart');
-  Dart2js.compile(context, srcFile, outDir: BUILD_TEST_DIR, minify: true);
-  File outFile = joinFile(BUILD_TEST_DIR, ['web_test.dart.js']);
+  File srcFile = new File('example/example.dart');
+  Dart2js.compile(srcFile, outDir: _buildExampleDir, minify: true);
+  File outFile = joinFile(_buildExampleDir, ['example.dart.js']);
 
   context.log('${outFile.path} compiled to ${_printSize(outFile)}');
 }
 
-/// Delete all generated artifacts.
-void clean(GrinderContext context) {
+@Task('Delete all generated artifacts')
+void clean() {
   // Delete the build/ dir.
-  deleteEntity(BUILD_DIR, context);
+  delete(buildDir);
 }
 
 String _printSize(File file) => '${(file.lengthSync() + 1023) ~/ 1024}k';