Update charted to 0.4.8 and roll

packages/barback/CHANGELOG.md

+## 0.15.2+11
+
+* Update `AssetNode.whenAvailable` to be a generic method to fix a new strong
+  mode error.
+
+## 0.15.2+10
+
+* Update `CancelableFuture` to match the new `Future.then` type signature. The
+  `onValue` parameter now has a return type of `FutureOr<S>` instead of
+  `S`.
+
+## 0.15.2+9
+
+* Fix all strong-mode warnings in Dart 1.18.
+
+## 0.15.2+8
+
+* Fix all strong-mode warnings in Dart 1.16.
+
 ## 0.15.2+7
 
 * Add periodic fine-grained logging for long running transformers.
 
 ## 0.15.2+6
 
 * Fix a deadlock that occurred occasionally when a declaring transformer was
   followed by a lazy transformer (most commonly `$dart2js`).
 
 ## 0.15.2+5
@@ skipping 143 matching lines @@
 
 * If a transformer calls `Transform.logger.error`, the transformer will now be
   considered to have failed after it finishes running `apply()`. This means that
   its outputs will not be consumed by future transformers and its primary input
   will not be passed through to the next phase.
 
 * If a transform calls `Transform.getInput`, `Transform.readInput`,
   `Transform.readInputAsString`, or `Transform.hasInput` on an input that
   doesn't exist, the transform will be re-run if that input is created in the
   future.