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

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 VM_ISOLATE_H_
 #define VM_ISOLATE_H_
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/atomic.h"
@@ skipping 429 matching lines @@
     ASSERT(!has_compiled());
     flags_.type_checks_ = true;
     flags_.asserts_ = true;
     flags_.error_on_bad_type_ = true;
     flags_.error_on_bad_override_ = true;
   }
 
   // Requests that the debugger resume execution.
   void Resume() {
     resume_request_ = true;
+    last_resume_timestamp_ = OS::GetCurrentTimeMillis();
+  }
+
+  int64_t last_resume_timestamp() const {
+    return last_resume_timestamp_;
   }
 
   // Returns whether the vm service has requested that the debugger
   // resume execution.
   bool GetAndClearResumeRequest() {
     bool resume_request = resume_request_;
     resume_request_ = false;
     return resume_request;
   }
 
@@ skipping 336 matching lines @@
   Heap* heap_;
   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 single_step_;
   bool resume_request_;
+  int64_t last_resume_timestamp_;
   bool has_compiled_;
   Flags flags_;
   Random random_;
   Simulator* simulator_;
   TimerList timer_list_;
   intptr_t deopt_id_;
   Mutex* mutex_;  // protects stack_limit_ and saved_stack_limit_.
   uword stack_limit_;
   uword saved_stack_limit_;
   uword stack_base_;
@@ skipping 253 matching lines @@
   uint8_t* serialized_message_;
   intptr_t serialized_message_len_;
   Isolate::Flags isolate_flags_;
   bool paused_;
   bool errors_are_fatal_;
 };
 
 }  // namespace dart
 
 #endif  // VM_ISOLATE_H_