Include constants in deferred computation.

pkg/compiler/lib/src/constants/expressions.dart

Index: pkg/compiler/lib/src/constants/expressions.dart
diff --git a/pkg/compiler/lib/src/constants/expressions.dart b/pkg/compiler/lib/src/constants/expressions.dart
index 2ea05a8794e629066e28dc7360fbd9f50229cc52..6fc55de309e57f4e65e9bc9a6818f3becb44821c 100644
--- a/pkg/compiler/lib/src/constants/expressions.dart
+++ b/pkg/compiler/lib/src/constants/expressions.dart
@@ -133,7 +133,7 @@ abstract class ConstantExpression {
   /// if it contains positional or named references, used to define constant
   /// constructors.
   // TODO(johnniwinther): Maybe make this final if we use it outside assertions.
-  bool get isPotential => true;
+  bool get isPotential => false;
 }
 
 /// A synthetic constant used to recover from errors.
@@ -195,9 +195,6 @@ class SyntheticConstantExpression extends ConstantExpression {
   ConstantExpressionKind get kind => ConstantExpressionKind.SYNTHETIC;
 
   @override
-  bool get isPotential => false;
-
-  @override
   bool get isImplicit => false;
 }
 
@@ -1270,9 +1267,7 @@ class PositionalArgumentReference extends ConstantExpression {
   }
 
   @override
-  bool get isPotential {
-    return true;
-  }
+  bool get isPotential => true;
 }
 
 /// A reference to a named parameter.
@@ -1311,9 +1306,7 @@ class NamedArgumentReference extends ConstantExpression {
   }
 
   @override
-  bool get isPotential {
-    return true;
-  }
+  bool get isPotential => true;
 }
 
 abstract class FromEnvironmentConstantExpression extends ConstantExpression {