Specs: fix typos in style2.md, checkin forgotten builtins.md, add guard feature to runloop.md, rena…

sky/specs/runloop.md

Index: sky/specs/runloop.md
diff --git a/sky/specs/runloop.md b/sky/specs/runloop.md
index a9b9e9e0d51a45353c92d234d571cfdec7569a12..b080090af1b1d6b4e2fe487d21d4fd569b36bbe2 100644
--- a/sky/specs/runloop.md
+++ b/sky/specs/runloop.md
@@ -11,6 +11,18 @@ fired.
 class DeadlineExceededException implements Exception { }
 ```
 
+There is a method you can use that guards your code against these
+exceptions:
+
+```dart
+typedef void Callback();
+external guardAgainstDeadlineExceptions(Callback callback);
+// runs callback.
+// if the time budget for the _task_ expires while the callback is
+// running, the callback isn't interrupted, but the method will throw
+// an exception once the callback returns.
+```
+
 When Sky is to *process a task queue until a particular time*, with a
 queue *relevant task queue*, bits *filter bits*, a time
 *particular time*, and an *idle rule* which is either "sleep" or