Fixed compilation time measurement, restructure some code.

runtime/vm/flow_graph_compiler_x64.h

 // Copyright (c) 2012, 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.
 
 #ifndef VM_FLOW_GRAPH_COMPILER_X64_H_
 #define VM_FLOW_GRAPH_COMPILER_X64_H_
 
 #ifndef VM_FLOW_GRAPH_COMPILER_H_
 #error Include flow_graph_compiler.h instead of flow_graph_compiler_x64.h.
 #endif
@@ skipping 21 matching lines @@
 
   void CompileGraph();
 
   // Infrastructure copied from class CodeGenerator or stubbed out.
   void FinalizePcDescriptors(const Code& code);
   void FinalizeStackmaps(const Code& code);
   void FinalizeVarDescriptors(const Code& code);
   void FinalizeExceptionHandlers(const Code& code);
 
  private:
+  // Constructor is lighweight, major initialization work should occur here.
+  // This makes it easier to measure time spent in the compiler.
+  void InitCompiler();
+
   struct BlockInfo : public ZoneAllocated {
    public:
     BlockInfo() : label() { }
 
     Label label;
   };
 
   BlockEntryInstr* current_block() const { return current_block_; }
 
   bool is_optimizing() const { return is_optimizing_; }
@@ skipping 86 matching lines @@
   DescriptorList* pc_descriptors_list_;
   ExceptionHandlerList* exception_handlers_list_;
   const bool is_optimizing_;
 
   DISALLOW_COPY_AND_ASSIGN(FlowGraphCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_FLOW_GRAPH_COMPILER_X64_H_