Added a run state field to Isolate

runtime/vm/isolate.h

Index: runtime/vm/isolate.h
===================================================================
--- runtime/vm/isolate.h	(revision 21380)
+++ runtime/vm/isolate.h	(working copy)
@@ -273,6 +273,11 @@
         kVmStatusInterrupt,
   };
 
+  enum IsolateRunState {
+    kIsolateWaiting = 0,      // The isolate is waiting for code to execute.
+    kIsolateRunning,          // The isolate is executing code.
+  };
+
   void ScheduleInterrupts(uword interrupt_bits);
   uword GetAndClearInterrupts();
 
@@ -285,6 +290,9 @@
   bool is_runnable() const { return is_runnable_; }
   void set_is_runnable(bool value) { is_runnable_ = value; }
 
+  IsolateRunState running_state() const { return running_state_; }
+  void set_running_state(IsolateRunState value) { running_state_ = value; }
+
   uword spawn_data() const { return spawn_data_; }
   void set_spawn_data(uword value) { spawn_data_ = value; }
 
@@ -492,6 +500,7 @@
   MessageHandler* message_handler_;
   uword spawn_data_;
   bool is_runnable_;
+  IsolateRunState running_state_;
   GcPrologueCallbacks gc_prologue_callbacks_;
   GcEpilogueCallbacks gc_epilogue_callbacks_;
 
@@ -607,6 +616,29 @@
   char* exception_callback_name_;
 };
 
+
+class IsolateRunStateManager : public StackResource {
+ public:
+  explicit IsolateRunStateManager()
+      : StackResource(Isolate::Current()),
+        saved_state_(Isolate::kIsolateWaiting) {
+    saved_state_ = reinterpret_cast<Isolate*>(isolate())->running_state();
+  }
+
+  virtual ~IsolateRunStateManager() {
+    reinterpret_cast<Isolate*>(isolate())->set_running_state(saved_state_);
+  }
+
+  void SetRunState(Isolate::IsolateRunState run_state) {
+    reinterpret_cast<Isolate*>(isolate())->set_running_state(run_state);
+  }
+
+ private:
+  Isolate::IsolateRunState saved_state_;
+
+  DISALLOW_COPY_AND_ASSIGN(IsolateRunStateManager);
+};
+
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_