Reapply r13292 WITH a fix to apply_test.dart that was failing on dartc

lib/core/function.dart

Index: lib/core/function.dart
===================================================================
--- lib/core/function.dart	(revision 13334)
+++ lib/core/function.dart	(working copy)
@@ -4,5 +4,30 @@
 
 // Dart core library.
 
+/**
+ * Super-type of all function types.
+ *
+ * A function value, or an instance of a class with a "call" method, is a
+ * subtype of a function type, and as such, a subtype of [Function].
+ */
 abstract class Function {
+  /**
+   * Dynamically call [function] with the specified arguments.
+   *
+   * Acts the same as calling function with positional arguments
+   * corresponding to the elements of [positionalArguments] and
+   * named arguments corresponding to the elements of [namedArguments].
+   *
+   * This includes giving the same errors if [function] isn't callable or
+   * if it expects different parameters.
+   *
+   * Example: [: Function.apply(foo, [1,2,3], {"f": 4, "g": 5}) :] gives
+   * exactly the same result as [: foo(1, 2, 3, f: 4, g: 5) :].
+   *
+   * If [positionalArguments] is null, it's considered an empty list.
+   * If [namedArguments] is omitted or null, it is considered an empty map.
+   */
+  external static apply(Function function,
+                        List positionalArguments,
+                        [Map<String,Dynamic> namedArguments]);
 }