Improve type optimization reusing the type argument vector of the instantiator

runtime/vm/flow_graph_optimizer.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/flow_graph_optimizer.h"
 
 #include "vm/bit_vector.h"
 #include "vm/cha.h"
 #include "vm/flow_graph_builder.h"
 #include "vm/flow_graph_compiler.h"
@@ skipping 4534 matching lines @@
     SetValue(instr, non_constant_);
     return;
   }
   if (IsConstant(object)) {
     const intptr_t len = instr->type_arguments().Length();
     if (instr->type_arguments().IsRawInstantiatedRaw(len) &&
         object.IsNull()) {
       SetValue(instr, object);
       return;
     }
-    if (instr->type_arguments().IsUninstantiatedIdentity() &&
-        !object.IsNull() &&
-        object.IsTypeArguments() &&
-        (TypeArguments::Cast(object).Length() == len)) {
+    if (instr->type_arguments().IsUninstantiatedIdentity()) {
       SetValue(instr, object);
       return;
     }
     SetValue(instr, non_constant_);
   }
 }
 
 
 void ConstantPropagator::VisitExtractConstructorTypeArguments(
     ExtractConstructorTypeArgumentsInstr* instr) {
@@ skipping 813 matching lines @@
   if (changed) {
     // We may have changed the block order and the dominator tree.
     flow_graph->DiscoverBlocks();
     GrowableArray<BitVector*> dominance_frontier;
     flow_graph->ComputeDominators(&dominance_frontier);
   }
 }
 
 
 }  // namespace dart