Remember when an isolate was paused and subtly display it in Obseravatory

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 337 matching lines @@
     kIsolateInterrupted = 6,
   };
 
   explicit DebuggerEvent(Isolate* isolate, EventType event_type)
       : isolate_(isolate),
         type_(event_type),
         top_frame_(NULL),
         breakpoint_(NULL),
         exception_(NULL),
         async_continuation_(NULL),
-        at_async_jump_(false) {}
+        at_async_jump_(false),
+        timestamp_(-1) {}
 
   Isolate* isolate() const { return isolate_; }
 
   EventType type() const { return type_; }
 
   bool IsPauseEvent() const {
     return (type_ == kBreakpointReached ||
             type_ == kIsolateInterrupted ||
             type_ == kExceptionThrown);
   }
@@ skipping 38 matching lines @@
     return at_async_jump_;
   }
   void set_at_async_jump(bool value) {
     at_async_jump_ = value;
   }
 
   Dart_Port isolate_id() const {
     return isolate_->main_port();
   }
 
+  void UpdateTimestamp();
+
+  int64_t timestamp() const {
+    return timestamp_;
+  }
+
  private:
   Isolate* isolate_;
   EventType type_;
   ActivationFrame* top_frame_;
   Breakpoint* breakpoint_;
   const Object* exception_;
   const Object* async_continuation_;
   bool at_async_jump_;
+  int64_t timestamp_;
 };
 
 
 class Debugger {
  public:
   typedef void EventHandler(DebuggerEvent* event);
 
   Debugger();
   ~Debugger();
 
@@ skipping 224 matching lines @@
 
   friend class Isolate;
   friend class BreakpointLocation;
   DISALLOW_COPY_AND_ASSIGN(Debugger);
 };
 
 
 }  // namespace dart
 
 #endif  // VM_DEBUGGER_H_