dart2js cps: Refactor tracking of side effects.

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 295cd3b9bfbbee008e9a062272e2e796055f26d5..575164434e0b6a2084b0e34ca04b08094fa504d7 100644
--- a/pkg/compiler/lib/src/cps_ir/builtin_operator.dart
+++ b/pkg/compiler/lib/src/cps_ir/builtin_operator.dart
@@ -5,6 +5,8 @@ library builtin_operator;
 // This is shared by the CPS and Tree IRs.
 // Both cps_ir_nodes and tree_ir_nodes import and re-export this file.
 
+import 'effects.dart';
+
 /// An operator supported natively in the CPS and Tree IRs using the
 /// `ApplyBuiltinOperator` instructions.
 ///
@@ -222,3 +224,17 @@ bool isCompoundableOperator(BuiltinOperator operator) {
       return false;
   }
 }
+
+int getEffectsOfBuiltinMethod(BuiltinMethod method) {
+  switch (method) {
+    case BuiltinMethod.Push:
+      return Effects.changesIndexableContent |
+             Effects.changesIndexableLength;
+    case BuiltinMethod.Pop:
+      return Effects.dependsOnIndexableContent |
+             Effects.dependsOnIndexableLength |
+             Effects.changesIndexableLength;
+    case BuiltinMethod.SetLength:
+      return Effects.changesIndexableLength;
+  }
+}