Document errorsAreFatal, onExit, onError in Changelog

CHANGELOG.md

 ## 1.13.0
 
 * `dart:core`
   * `Uri` added `removeFragment` method.
   * `String.allMatches` (implementing `Pattern.allMatches`) is now lazy,
     as all `allMatches` implementations are intended to be.
 * `dart:io`
   * `HttpClient` no longer sends URI fragments in the requeust. This is not
     allowed by the HTTP protocol.
     The `HttpServer` still gracefully receives fragments, but discards them
@@ skipping 27 matching lines @@
     `setInnerHtml` or other methods that create DOM from text. It is
     also more efficient, skipping the creation of a `DocumentFragment`.
 
 * `dart:io`
   * Added two new file modes, `WRITE_ONLY` and `WRITE_ONLY_APPEND` for
     opening a file write only.
     [eaeecf2](https://github.com/dart-lang/sdk/commit/eaeecf2ed13ba6c7fbfd653c3c592974a7120960)
   * Change stdout/stderr to binary mode on Windows.
     [4205b29](https://github.com/dart-lang/sdk/commit/4205b2997e01f2cea8e2f44c6f46ed6259ab7277)
 
+* `dart:isolate`
+  * Added `onError`, `onExit` and `errorsAreFatal` parameters to
+    `Isolate.spawnUri`.
+
 * `dart:mirrors`
   * `InstanceMirror.delegate` moved up to `ObjectMirror`.
 
 ### Tool changes
 
 * Pub
 
   * **Breaking:** various commands that previously ran `pub get` implicitly no
     longer do so. Instead, they merely check to make sure the ".packages" file
     is newer than the pubspec and the lock file, and fail if it's not.
@@ skipping 430 matching lines @@
     they will keep the Dart process alive until they time out. This fixes the
     handling of persistent connections. Previously, the client would shut down
     immediately after a request.
 
   * **Breaking change:** `HttpServer` no longer compresses all traffic by
     default. The new `autoCompress` property can be set to `true` to re-enable
     compression.
 
 * `dart:isolate`: `Isolate.spawnUri` added the optional `packageRoot` argument,
   which controls how it resolves `package:` URIs.