dart2js cps: Rewrite more List operations into JS array operations.

pkg/compiler/lib/src/cps_ir/builtin_operator.dart

Index: pkg/compiler/lib/src/cps_ir/builtin_operator.dart
diff --git a/pkg/compiler/lib/src/cps_ir/builtin_operator.dart b/pkg/compiler/lib/src/cps_ir/builtin_operator.dart
index 9077c9f118c3974d3ea489f9e30530a363e1037b..28397eb68bc52a7f7558c4a456f6ffb850a98cc7 100644
--- a/pkg/compiler/lib/src/cps_ir/builtin_operator.dart
+++ b/pkg/compiler/lib/src/cps_ir/builtin_operator.dart
@@ -104,3 +104,29 @@ enum BuiltinOperator {
   /// Compiles to `typeof x === 'number' && Math.floor(x) === x`
   IsNumberAndFloor,
 }
+
+/// A method supported natively in the CPS and Tree IRs using the
+/// `ApplyBuiltinMethod` instructions.
+/// 
+/// These methods all operate on a distinguished 'object' argument, and
+/// take zero or more additional arguments.
+/// 
+/// These methods may mutate and depend on the state of the object argument,
+/// but may not depend on or mutate any other state. An exception is thrown
+/// if the object is null, but otherwise they cannot throw or diverge.
+enum BuiltinMethod {
+  /// Add an item to a native list.
+  /// 
+  /// Takes any number of arguments, each argument will be added to the
+  /// list on the order given (as per the JS `push` method).
+  /// 
+  /// Compiles to `object.push(x1, ..., xN)`.
+  Push,
+
+  /// Remove and return the last item from a native list.
+  /// 
+  /// Takes no arguments.
+  /// 
+  /// Compiles to `object.pop()`.
+  Pop,
+}