Stub implementation of patch invariants for the patch refactoring.

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 f71632d0c8c147c6402d0052c5cb914cff678647..289b048b7984e0ae7ea4bce32001d01b476a39c2 100644
--- a/lib/compiler/implementation/ssa/nodes.dart
+++ b/lib/compiler/implementation/ssa/nodes.dart
@@ -2367,7 +2367,10 @@ class HThrow extends HControlFlow {
 
 class HStatic extends HInstruction {
   final Element element;
-  HStatic(this.element) : super(<HInstruction>[]) { assert(element !== null); }
+  HStatic(this.element) : super(<HInstruction>[]) {
+    assert(element !== null);
+    assert(element.isDeclaration);
+  }
 
   void prepareGvn(HTypeMap types) {
     if (!element.isAssignable()) {