PredictableCodeSizeScope checks the expected size now.

src/assembler.h

 // Copyright (c) 1994-2006 Sun Microsystems Inc.
 // All Rights Reserved.
 //
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 // - Redistributions of source code must retain the above copyright notice,
 // this list of conditions and the following disclaimer.
 //
@@ skipping 80 matching lines @@
   int jit_cookie_;
   bool emit_debug_code_;
   bool predictable_code_size_;
 };
 
 
 // Avoids using instructions that vary in size in unpredictable ways between the
 // snapshot and the running VM.
 class PredictableCodeSizeScope {
  public:
-  explicit PredictableCodeSizeScope(AssemblerBase* assembler)
-      : assembler_(assembler) {
-    old_value_ = assembler_->predictable_code_size();
-    assembler_->set_predictable_code_size(true);
-  }
-
-  ~PredictableCodeSizeScope() {
-    assembler_->set_predictable_code_size(old_value_);
-  }
+  PredictableCodeSizeScope(AssemblerBase* assembler, int expected_size);
+  ~PredictableCodeSizeScope();
 
  private:
   AssemblerBase* assembler_;
+  int expected_size_;
+  int start_offset_;
   bool old_value_;
 };
 
 
 // -----------------------------------------------------------------------------
 // Labels represent pc locations; they are typically jump or call targets.
 // After declaration, a label can be freely used to denote known or (yet)
 // unknown pc location. Assembler::bind() is used to bind a label to the
 // current pc. A label can be bound only once.
 
@@ skipping 829 matching lines @@
  public:
   NullCallWrapper() { }
   virtual ~NullCallWrapper() { }
   virtual void BeforeCall(int call_size) const { }
   virtual void AfterCall() const { }
 };
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_