Eliminate dependencies on assemblers and code stubs in precompiled runtime.

runtime/vm/branch_optimizer.cc

 // Copyright (c) 2016, 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.
 
+#if !defined(DART_PRECOMPILED_RUNTIME)
+
 #include "vm/branch_optimizer.h"
 
 #include "vm/flow_graph.h"
 #include "vm/intermediate_language.h"
 
 namespace dart {
 
 // Returns true if the given phi has a single input use and
 // is used in the environments either at the corresponding block entry or
 // at the same instruction where input use is.
@@ skipping 326 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
+
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)