Add necessary support functions so that embedders can implemented pause on start and exit

runtime/vm/message_handler.h

 // Copyright (c) 2011, 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_MESSAGE_HANDLER_H_
 #define VM_MESSAGE_HANDLER_H_
 
 #include "vm/isolate.h"
 #include "vm/message.h"
 #include "vm/os_thread.h"
@@ skipping 38 matching lines @@
            EndCallback end_callback,
            CallbackData data);
 
   // Handles the next message for this message handler.  Should only
   // be used when not running the handler on the thread pool (via Run
   // or RunBlocking).
   //
   // Returns true on success.
   MessageStatus HandleNextMessage();
 
+  // Handles all normals messages for this message handler.  Should only

[turnidge, 2016/02/03 21:33:37]

Delete "normals".

This functions actually handles all messages, so consider naming it
HandleMessages or perhaps HandleAllMessages.

[Cutch, 2016/02/03 23:04:05]

Done.

+  // be used when not running the handler on the thread pool (via Run
+  // or RunBlocking).
+  //
+  // Returns true on success.
+  MessageStatus HandleNormalMessages();
+
   // Handles any OOB messages for this message handler.  Can be used
   // even if the message handler is running on the thread pool.
   //
   // Returns true on success.
   MessageStatus HandleOOBMessages();
 
   // Returns true if there are pending OOB messages for this message
   // handler.
   bool HasOOBMessages();
 
   // A message handler tracks how many live ports it has.
   bool HasLivePorts() const { return live_ports_ > 0; }
 
   intptr_t live_ports() const {
     return live_ports_;
   }
 
   bool paused() const { return paused_ > 0; }
 
   void increment_paused() { paused_++; }
   void decrement_paused() { ASSERT(paused_ > 0); paused_--; }
 
   bool pause_on_start() const {

[turnidge, 2016/02/03 21:33:37]

Consider renaming these to match your CL:

pause_on_start() -> ShouldPauseOnStart()
set_pause_on_start() -> SetShouldPauseOnStart()
paused_on_start() -> IsPausedOnStart(),

I think your new names are more clear than my old ones.

etc.

Perhaps rename the fields as well:

pause_on_start_ -> should_pause_on_start_.

You get the drill.

[Cutch, 2016/02/03 23:04:05]

Done.

     return pause_on_start_;
   }
 
   void set_pause_on_start(bool pause_on_start) {
     pause_on_start_ = pause_on_start;
   }
 
   bool paused_on_start() const {
     // If pause_on_start_ is still set, tell the user we are paused,
     // even if we haven't hit the pause point yet.
@@ skipping 10 matching lines @@
 
   bool paused_on_exit() const {
     return paused_on_exit_;
   }
 
   // Timestamp of the paused on start or paused on exit.
   int64_t paused_timestamp() const {
     return paused_timestamp_;
   }
 
+  void PausedOnStart(bool v);
+  void PausedOnExit(bool v);
+
   class AcquiredQueues : public ValueObject {
    public:
     AcquiredQueues();
 
     ~AcquiredQueues();
 
     MessageQueue* queue() {
       if (handler_ == NULL) {
         return NULL;
       }
@@ skipping 22 matching lines @@
 
 #if defined(DEBUG)
   // Check that it is safe to access this message handler.
   //
   // For example, if this MessageHandler is an isolate, then it is
   // only safe to access it when the MessageHandler is the current
   // isolate.
   virtual void CheckAccess();
 #endif
 
+  virtual void NotifyPauseOnStart() {}
+  virtual void NotifyPauseOnExit() {}
+
  protected:
   // ------------ START PortMap API ------------
   // These functions should only be called from the PortMap.
 
   // Does this message handler correspond to the current isolate?
   virtual bool IsCurrentIsolate() const { return false; }
 
   // Return Isolate to which this message handler corresponds to.
   virtual Isolate* isolate() const { return NULL; }
 
@@ skipping 18 matching lines @@
   // ------------ END PortMap API ------------
 
   // Custom message notification.  Optionally provided by subclass.
   virtual void MessageNotify(Message::Priority priority);
 
   // Handles a single message.  Provided by subclass.
   //
   // Returns true on success.
   virtual MessageStatus HandleMessage(Message* message) = 0;
 
-  virtual void NotifyPauseOnStart() {}
-  virtual void NotifyPauseOnExit() {}
-
   // TODO(iposva): Set a local field before entering MessageHandler methods.
   Thread* thread() const { return Thread::Current(); }
 
  private:
   friend class PortMap;
   friend class MessageHandlerTestPeer;
   friend class MessageHandlerTask;
 
   // Called by MessageHandlerTask to process our task queue.
   void TaskCallback();
 
+  void PausedOnStartLocked(bool v);
+  void PausedOnExitLocked(bool v);
+
   // Dequeue the next message.  Prefer messages from the oob_queue_ to
   // messages from the queue_.
   Message* DequeueMessage(Message::Priority min_priority);
 
   void ClearOOBQueue();
 
   // Handles any pending messages.
   MessageStatus HandleMessages(bool allow_normal_messages,
                                bool allow_multiple_normal_messages);
 
@@ skipping 15 matching lines @@
   StartCallback start_callback_;
   EndCallback end_callback_;
   CallbackData callback_data_;
 
   DISALLOW_COPY_AND_ASSIGN(MessageHandler);
 };
 
 }  // namespace dart
 
 #endif  // VM_MESSAGE_HANDLER_H_