Don't use === instead of equality-method call for user class constants.

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 03d2fb560490aa5ae50a7dcf06f92913bdcaa408..0ce41919a7a9e36b3abb1f8805cbbf3ce5fd4b7f 100644
--- a/lib/compiler/implementation/ssa/nodes.dart
+++ b/lib/compiler/implementation/ssa/nodes.dart
@@ -1843,7 +1843,12 @@ class HEquals extends HRelational {
   accept(HVisitor visitor) => visitor.visitEquals(this);
 
   bool get builtin() {
-    return (left.isNumber() && right.isNumber()) || left is HConstant;
+    if (left.isNumber() && right.isNumber()) return true;
+    if (left is !HConstant) return false;
+    HConstant leftConstant = left;
+    // TODO(floitsch): we can do better if we know that the constant does not
+    // have the equality operator overridden.
+    return !leftConstant.constant.isConstructedObject();
   }
 
   HType computeType() => HType.BOOLEAN;