Remove some Isolate::current_zone() calls, as it gets the zone from mutator thread not the current …

runtime/vm/debugger.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_DEBUGGER_H_
 #define VM_DEBUGGER_H_
 
 #include "include/dart_tools_api.h"
 
 #include "vm/object.h"
@@ skipping 632 matching lines @@
                             const Library& lib,
                             const String& prefix,
                             bool include_private_fields);
 
   // Handles any events which pause vm execution.  Breakpoints,
   // interrupts, etc.
   void Pause(DebuggerEvent* event);
 
   void HandleSteppingRequest(DebuggerStackTrace* stack_trace);
 
-  Zone* zone() const { return isolate_->current_zone(); }
+  Zone* zone() const {
+    ASSERT(isolate_->MutatorThreadIsCurrentThread());
+    return isolate_->current_zone();
+  }
 
   Isolate* isolate_;
   Dart_Port isolate_id_;  // A unique ID for the isolate in the debugger.
   bool initialized_;
 
   // ID number generator.
   intptr_t next_id_;
 
   BreakpointLocation* latent_locations_;
   BreakpointLocation* breakpoint_locations_;
@@ skipping 30 matching lines @@
 
   friend class Isolate;
   friend class BreakpointLocation;
   DISALLOW_COPY_AND_ASSIGN(Debugger);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DEBUGGER_H_