Fix a crash in debugger, add flag --stress-test-background-compilation, add asserts.

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 63 matching lines @@
  private:
   IndirectGotoInstr* backtrack_goto_;
 };
 
 
 class Compiler : public AllStatic {
  public:
   static const intptr_t kNoOSRDeoptId = Thread::kNoDeoptId;
 
   static bool IsBackgroundCompilation();
+  // The result for a function may change if debugging gets turned on/off.
+  static bool CanOptimizeFunction(Thread* thread, const Function& function);
 
   // Extracts top level entities from the script and populates
   // the class dictionary of the library.
   //
   // Returns Error::null() if there is no compilation error.
   static RawError* Compile(const Library& library, const Script& script);
 
   // Extracts function and field symbols from the class and populates
   // the class.
   //
@@ skipping 91 matching lines @@
   Monitor* done_monitor_;   // Notify/wait that the thread is done.
 
   BackgroundCompilationQueue* function_queue_;
 
   DISALLOW_IMPLICIT_CONSTRUCTORS(BackgroundCompiler);
 };
 
 }  // namespace dart
 
 #endif  // VM_COMPILER_H_