Remove support for non-ssa optimizing code generation.

runtime/vm/flow_graph_optimizer.h

Index: runtime/vm/flow_graph_optimizer.h
diff --git a/runtime/vm/flow_graph_optimizer.h b/runtime/vm/flow_graph_optimizer.h
index 2296bee4dfeb85171ebe0083362edcd907491b5e..b83b16b7cd1d5815a22b121a345fcdb58c822b9c 100644
--- a/runtime/vm/flow_graph_optimizer.h
+++ b/runtime/vm/flow_graph_optimizer.h
@@ -14,8 +14,8 @@ template <typename T> class GrowableArray;
 
 class FlowGraphOptimizer : public FlowGraphVisitor {
  public:
-  FlowGraphOptimizer(const FlowGraph& flow_graph, bool use_ssa)
-      : FlowGraphVisitor(flow_graph.reverse_postorder()), use_ssa_(use_ssa) {}
+  explicit FlowGraphOptimizer(const FlowGraph& flow_graph)
+      : FlowGraphVisitor(flow_graph.reverse_postorder()) {}
   virtual ~FlowGraphOptimizer() {}
 
   void ApplyICData();
@@ -47,8 +47,6 @@ class FlowGraphOptimizer : public FlowGraphVisitor {
 
   bool TryInlineInstanceMethod(BindInstr* instr, InstanceCallComp* comp);
 
-  bool use_ssa_;
-
   DISALLOW_COPY_AND_ASSIGN(FlowGraphOptimizer);
 };
 
@@ -78,11 +76,9 @@ class ParsedFunction;
 
 class FlowGraphTypePropagator : public FlowGraphVisitor {
  public:
-  explicit FlowGraphTypePropagator(const FlowGraph& flow_graph,
-                                   bool is_ssa)
+  explicit FlowGraphTypePropagator(const FlowGraph& flow_graph)
       : FlowGraphVisitor(flow_graph.reverse_postorder()),
         parsed_function_(flow_graph.parsed_function()),
-        is_ssa_(is_ssa),
         still_changing_(false) { }
   virtual ~FlowGraphTypePropagator() { }
 
@@ -104,8 +100,6 @@ class FlowGraphTypePropagator : public FlowGraphVisitor {
 
  private:
   const ParsedFunction& parsed_function_;
-  const bool is_ssa_;  // TODO(regis): Remove once virtual frame backend is
-                       // removed.
   bool still_changing_;
   DISALLOW_COPY_AND_ASSIGN(FlowGraphTypePropagator);
 };