Clean up CodeObservers

runtime/vm/code_observers.h

Index: runtime/vm/code_observers.h
diff --git a/runtime/vm/code_observers.h b/runtime/vm/code_observers.h
index 1891f3dd78a41d3234397ae060e974b90cc67aff..aefc85af0fca06126fd70bcb08398939c8c8b1ca 100644
--- a/runtime/vm/code_observers.h
+++ b/runtime/vm/code_observers.h
@@ -6,6 +6,7 @@
 #define VM_CODE_OBSERVERS_H_
 
 #include "vm/globals.h"
+#include "vm/allocation.h"
 
 namespace dart {
 
@@ -29,7 +30,7 @@ class CodeObserver {
 };
 
 
-class CodeObservers {
+class CodeObservers : public AllStatic {
  public:
   static void InitOnce();
 
@@ -45,6 +46,8 @@ class CodeObservers {
   // Returns true if there is at least one active code observer.
   static bool AreActive();
 
+  static void DeleteAll();
+
  private:
   static intptr_t observers_length_;
   static CodeObserver** observers_;