Refactor building of StoreStaticField and StoreLocal to manually preserve value.

runtime/vm/parser.cc

Index: runtime/vm/parser.cc
diff --git a/runtime/vm/parser.cc b/runtime/vm/parser.cc
index 95efcf223f0c70f0efccc3a2c2dc09f6324fe959..2340bf36c020e3811a01e3e5cde2c3a83d65bb48 100644
--- a/runtime/vm/parser.cc
+++ b/runtime/vm/parser.cc
@@ -6744,7 +6744,9 @@ AstNode* Parser::CreateAssignmentNode(AstNode* original, AstNode* rhs) {
   if ((result != NULL) &&
       (result->IsStoreIndexedNode() ||
        result->IsInstanceSetterNode() ||
-       result->IsStaticSetterNode())) {
+       result->IsStaticSetterNode() ||
+       result->IsStoreStaticFieldNode() ||
+       result->IsStoreLocalNode())) {
     EnsureExpressionTemp();
   }
   return result;