Big merge from experimental to bleeding edge.

sdk/lib/core/errors.dart

Index: sdk/lib/core/errors.dart
diff --git a/sdk/lib/core/errors.dart b/sdk/lib/core/errors.dart
index 5fbd2d99df880cd324ea1d50c0d3452f8fac8f1a..59f30d039198f5e711bdeaaea11d486aa1ce8067 100644
--- a/sdk/lib/core/errors.dart
+++ b/sdk/lib/core/errors.dart
@@ -196,8 +196,8 @@ class NoSuchMethodError implements Error {
 /**
  * The operation was not allowed by the object.
  *
- * This [Error] is thrown when a class cannot implement
- * one of the methods in its signature.
+ * This [Error] is thrown when an instance cannot implement one of the methods
+ * in its signature.
  */
 class UnsupportedError implements Error {
   final String message;