Introduce DontEmitDebugCodeScope to fix the x64 nosnapshot build.

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 89 matching lines @@
 
  private:
   Isolate* isolate_;
   int jit_cookie_;
   uint64_t enabled_cpu_features_;
   bool emit_debug_code_;
   bool predictable_code_size_;
 };
 
 
+// Avoids emitting debug code during the lifetime of this scope object.
+class DontEmitDebugCodeScope BASE_EMBEDDED {
+ public:
+  explicit DontEmitDebugCodeScope(AssemblerBase* assembler)
+      : assembler_(assembler), old_value_(assembler->emit_debug_code()) {
+    assembler_->set_emit_debug_code(false);
+  }
+  ~DontEmitDebugCodeScope() {
+    assembler_->set_emit_debug_code(old_value_);
+  };
+ private:
+  AssemblerBase* assembler_;
+  bool old_value_;
+};
+
+
 // Avoids using instructions that vary in size in unpredictable ways between the
 // snapshot and the running VM.
 class PredictableCodeSizeScope {
  public:
   PredictableCodeSizeScope(AssemblerBase* assembler, int expected_size);
   ~PredictableCodeSizeScope();
 
  private:
   AssemblerBase* assembler_;
   int expected_size_;
@@ skipping 962 matching lines @@
 
  private:
   int32_t multiplier_;
   int32_t shift_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_ASSEMBLER_H_