Eliminate dependencies on assemblers and code stubs in precompiled runtime.

runtime/vm/flow_graph.cc

Index: runtime/vm/flow_graph.cc
diff --git a/runtime/vm/flow_graph.cc b/runtime/vm/flow_graph.cc
index 9314d92018da1d8d949ed4793cb5599bb6122968..eb0b2cb57a09d005feb0bf23ec281606a2ba217e 100644
--- a/runtime/vm/flow_graph.cc
+++ b/runtime/vm/flow_graph.cc
@@ -2,6 +2,8 @@
 // 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/flow_graph.h"
 
 #include "vm/bit_vector.h"
@@ -2347,3 +2349,5 @@ void FlowGraph::AppendExtractNthOutputForMerged(Definition* instr,
 
 
 }  // namespace dart
+
+#endif  // !defined(DART_PRECOMPILED_RUNTIME)