Make the lock/unlock and Enter/Exit methods in Mutex and Monitor private so taht we always use the …

runtime/vm/message_handler_test.cc

Index: runtime/vm/message_handler_test.cc
diff --git a/runtime/vm/message_handler_test.cc b/runtime/vm/message_handler_test.cc
index 314eb7c275c5b6f07f0b68b3f77b99905f9b77e7..e6a39a6680468a61475796e077415df1fc72ba1f 100644
--- a/runtime/vm/message_handler_test.cc
+++ b/runtime/vm/message_handler_test.cc
@@ -165,8 +165,7 @@ UNIT_TEST_CASE(MessageHandler_HasOOBMessages) {
   EXPECT(!handler.HasOOBMessages());
   {
     // Acquire ownership of message handler queues, verify one regular message.
-    MessageHandler::AcquiredQueues aq;
-    handler.AcquireQueues(&aq);
+    MessageHandler::AcquiredQueues aq(&handler);
     EXPECT(aq.queue()->Length() == 1);
   }
 
@@ -177,8 +176,7 @@ UNIT_TEST_CASE(MessageHandler_HasOOBMessages) {
   {
     // Acquire ownership of message handler queues, verify one regular and one
     // OOB message.
-    MessageHandler::AcquiredQueues aq;
-    handler.AcquireQueues(&aq);
+    MessageHandler::AcquiredQueues aq(&handler);
     EXPECT(aq.queue()->Length() == 1);
     EXPECT(aq.oob_queue()->Length() == 1);
   }
@@ -308,8 +306,7 @@ UNIT_TEST_CASE(MessageHandler_HandleNextMessage_Shutdown) {
   EXPECT_EQ(port3, ports[1]);  // oob_message2, shutdown
   {
     // The oob queue has been cleared.  oob_message3 is gone.
-    MessageHandler::AcquiredQueues aq;
-    handler.AcquireQueues(&aq);
+    MessageHandler::AcquiredQueues aq(&handler);
     EXPECT(aq.oob_queue()->Length() == 0);
   }
   handler_peer.CloseAllPorts();