Postpone the argument type optimizations until the types are stable.

lib/compiler/implementation/ssa/nodes.dart

Index: lib/compiler/implementation/ssa/nodes.dart
diff --git a/lib/compiler/implementation/ssa/nodes.dart b/lib/compiler/implementation/ssa/nodes.dart
index df6816a2b52aa782edcdf66e488fbe42205dfb4d..90864821daf3ca4536c4c92c560ffa975d8d72f3 100644
--- a/lib/compiler/implementation/ssa/nodes.dart
+++ b/lib/compiler/implementation/ssa/nodes.dart
@@ -935,12 +935,12 @@ class HInstruction implements Hashable {
   bool isConstantBoolean() => false;
   bool isConstantNull() => false;
   bool isConstantNumber() => false;
+  bool isConstantInteger() => false;
   bool isConstantString() => false;
   bool isConstantList() => false;
   bool isConstantMap() => false;
   bool isConstantFalse() => false;
   bool isConstantTrue() => false;
-  bool isConstantInteger() => false;
 
   bool isValid() {
     HValidator validator = new HValidator();