Remove some dead fields from Isolate.

runtime/vm/isolate.h

 // Copyright (c) 2013, 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 RUNTIME_VM_ISOLATE_H_
 #define RUNTIME_VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 717 matching lines @@
 
   // Accessed from generated code:
   StoreBuffer* store_buffer_;
   Heap* heap_;
   uword user_tag_;
   RawUserTag* current_tag_;
   RawUserTag* default_tag_;
   RawCode* ic_miss_code_;
   ClassTable class_table_;
   bool single_step_;
-  bool skip_step_;  // skip the next single step.
 
   ThreadRegistry* thread_registry_;
   SafepointHandler* safepoint_handler_;
   Dart_MessageNotifyCallback message_notify_callback_;
   char* name_;
   char* debugger_name_;
   int64_t start_time_;
   Dart_Port main_port_;
   Dart_Port origin_id_;  // Isolates created by spawnFunc have some origin id.
   uint64_t pause_capability_;
   uint64_t terminate_capability_;
   bool errors_fatal_;
   ObjectStore* object_store_;
-  uword top_exit_frame_info_;
   void* init_callback_data_;
   Dart_EnvironmentCallback environment_callback_;
   Dart_LibraryTagHandler library_tag_handler_;
   ApiState* api_state_;
   Debugger* debugger_;
   bool resume_request_;
   int64_t last_resume_timestamp_;
   bool has_compiled_code_;  // Can check that no compilation occured.
   Random random_;
   Simulator* simulator_;
@@ skipping 14 matching lines @@
   bool is_service_isolate_;
 
   // Isolate-specific flags.
   NOT_IN_PRODUCT(
     bool type_checks_;
     bool asserts_;
     bool error_on_bad_type_;
     bool error_on_bad_override_;
   )
 
-  // Status support.
-  char* stacktrace_;
-  intptr_t stack_frame_index_;
-
   // Timestamps of last operation via service.
   int64_t last_allocationprofile_accumulator_reset_timestamp_;
   int64_t last_allocationprofile_gc_timestamp_;
 
   // Ring buffer of objects assigned an id.
   ObjectIdRing* object_id_ring_;
 
   VMTagCounters vm_tag_counters_;
   RawGrowableObjectArray* tag_table_;
 
@@ skipping 222 matching lines @@
   intptr_t* spawn_count_;
 
   Dart_IsolateFlags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // RUNTIME_VM_ISOLATE_H_