Store and serialize NativeBehavior in TreeElements.

pkg/compiler/lib/src/universe/side_effects.dart

Index: pkg/compiler/lib/src/universe/side_effects.dart
diff --git a/pkg/compiler/lib/src/universe/side_effects.dart b/pkg/compiler/lib/src/universe/side_effects.dart
index 2c39999dddec2a30f4605d97a581eea46b3e6e7e..280d56abac6dfdf80293d638e57cf46303ab5cc0 100644
--- a/pkg/compiler/lib/src/universe/side_effects.dart
+++ b/pkg/compiler/lib/src/universe/side_effects.dart
@@ -33,6 +33,8 @@ class SideEffects {
     clearAllSideEffects();
   }
 
+  SideEffects.fromFlags(this._flags);
+
   bool operator ==(other) => _flags == other._flags;
 
   int get hashCode => throw new UnsupportedError('SideEffects.hashCode');
@@ -147,6 +149,8 @@ class SideEffects {
     _flags = other._flags;
   }
 
+  int get flags => _flags;
+
   String toString() {
     StringBuffer buffer = new StringBuffer();
     buffer.write('Depends on');