Prepare for computation of NewStructure in Resolution.

pkg/compiler/lib/src/elements/modelx.dart

Index: pkg/compiler/lib/src/elements/modelx.dart
diff --git a/pkg/compiler/lib/src/elements/modelx.dart b/pkg/compiler/lib/src/elements/modelx.dart
index 33410f7637a4cbc13514ed46903b90f3c1226d1a..8381dfad57b6c593d2adec2e9980bad9bc382dff 100644
--- a/pkg/compiler/lib/src/elements/modelx.dart
+++ b/pkg/compiler/lib/src/elements/modelx.dart
@@ -2325,7 +2325,11 @@ abstract class BaseClassElementX extends ElementX
   bool get isEnumClass => false;
 
   InterfaceType computeType(Compiler compiler) {
-    if (thisTypeCache == null) {
+    if (isPatch) {
+      origin.computeType(compiler);
+      thisTypeCache = origin.thisType;
+      rawTypeCache = origin.rawType;
+    } else if (thisTypeCache == null) {
       computeThisAndRawType(compiler, computeTypeParameters(compiler));
     }
     return thisTypeCache;