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

runtime/vm/message_handler.h

Index: runtime/vm/message_handler.h
diff --git a/runtime/vm/message_handler.h b/runtime/vm/message_handler.h
index f4d907ca8765c0a0bb3cdd1ce0b801cd40d4cab4..d1ed89b1ede5c70bc4860992dfe7fa6dec2e65ff 100644
--- a/runtime/vm/message_handler.h
+++ b/runtime/vm/message_handler.h
@@ -56,6 +56,13 @@ class MessageHandler {
   // 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.
   //
@@ -109,6 +116,9 @@ class MessageHandler {
     return paused_timestamp_;
   }
 
+  void PausedOnStart(bool v);
+  void PausedOnExit(bool v);
+
   class AcquiredQueues : public ValueObject {
    public:
     AcquiredQueues();
@@ -151,6 +161,9 @@ class MessageHandler {
   virtual void CheckAccess();
 #endif
 
+  virtual void NotifyPauseOnStart() {}
+  virtual void NotifyPauseOnExit() {}
+
  protected:
   // ------------ START PortMap API ------------
   // These functions should only be called from the PortMap.
@@ -189,9 +202,6 @@ class MessageHandler {
   // 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(); }
 
@@ -203,6 +213,9 @@ class MessageHandler {
   // 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);