VM: Add infrastructure to support deferred generation of unoptimized code.

runtime/vm/compiler.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_COMPILER_H_
 #define VM_COMPILER_H_
 
 #include "vm/allocation.h"
 #include "vm/growable_array.h"
 #include "vm/runtime_entry.h"
@@ skipping 23 matching lines @@
   // the class.
   //
   // Returns Error::null() if there is no compilation error.
   static RawError* CompileClass(const Class& cls);
 
   // Generates code for given function and sets its code field.
   //
   // Returns Error::null() if there is no compilation error.
   static RawError* CompileFunction(Thread* thread, const Function& function);
 
+  // Generates unoptimized code if not present, current code is unchanged.
+  static void EnsureUnoptimizedCode(Thread* thread, const Function& function);
+
   // Generates optimized code for function.
   //
   // Returns Error::null() if there is no compilation error.
   static RawError* CompileOptimizedFunction(
       Thread* thread,
       const Function& function,
       intptr_t osr_id = Isolate::kNoDeoptId);
 
   // Generates code for given parsed function (without parsing it again) and
   // sets its code field.
@@ skipping 17 matching lines @@
 
   // Eagerly compiles all functions in a class.
   //
   // Returns Error::null() if there is no compilation error.
   static RawError* CompileAllFunctions(const Class& cls);
 };
 
 }  // namespace dart
 
 #endif  // VM_COMPILER_H_