Re-enable Dart_Api Timeline tracing

runtime/vm/timeline.h

 // Copyright (c) 2015, 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_TIMELINE_H_
 #define VM_TIMELINE_H_
 
 #include "vm/allocation.h"
 #include "vm/bitfield.h"
 #include "vm/os.h"
@@ skipping 51 matching lines @@
     return &stream_##name##_enabled_;                                          \
   }                                                                            \
   static void SetStream##name##Enabled(bool enabled) {                         \
     stream_##name##_enabled_ = enabled;                                        \
   }
   ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_FLAGS)
 #undef ISOLATE_TIMELINE_STREAM_FLAGS
 
  private:
   static TimelineEventRecorder* recorder_;
-  static TimelineStream* vm_stream_;
-  static TimelineStream* vm_api_stream_;
+  static TimelineStream vm_stream_;
+  static TimelineStream vm_api_stream_;
 
 #define ISOLATE_TIMELINE_STREAM_DECLARE_FLAG(name, not_used)                   \
   static bool stream_##name##_enabled_;
   ISOLATE_TIMELINE_STREAM_LIST(ISOLATE_TIMELINE_STREAM_DECLARE_FLAG)
 #undef ISOLATE_TIMELINE_STREAM_DECLARE_FLAG
 
   friend class TimelineRecorderOverride;
   friend class ReclaimBlocksIsolateVisitor;
 };
 
@@ skipping 659 matching lines @@
 
  private:
   TimelineEventBlock* current_;
   TimelineEventRecorder* recorder_;
 };
 
 
 }  // namespace dart
 
 #endif  // VM_TIMELINE_H_