Implement deoptimization in the SSA compiler as a parallel move.

runtime/vm/flow_graph_compiler_x64.h

Index: runtime/vm/flow_graph_compiler_x64.h
diff --git a/runtime/vm/flow_graph_compiler_x64.h b/runtime/vm/flow_graph_compiler_x64.h
index 19712640de77e0b8111e08f004a5de30ee9abf82..b0bbddd5d35ea93651d8dd27fd92f10584c48885 100644
--- a/runtime/vm/flow_graph_compiler_x64.h
+++ b/runtime/vm/flow_graph_compiler_x64.h
@@ -50,6 +50,9 @@ class FlowGraphCompiler : public ValueObject {
   static bool CanOptimize();
   bool is_optimizing() const { return is_optimizing_; }
   const GrowableArray<BlockInfo*>& block_info() const { return block_info_; }
+  ParallelMoveResolver* parallel_move_resolver() {
+    return &parallel_move_resolver_;
+  }
 
   // Constructor is lighweight, major initialization work should occur here.
   // This makes it easier to measure time spent in the compiler.