Introduce a kSetEventMaskCommand, some cleanups in windows eventhandler

dart/runtime/bin/eventhandler_macos.cc

Index: dart/runtime/bin/eventhandler_macos.cc
diff --git a/dart/runtime/bin/eventhandler_macos.cc b/dart/runtime/bin/eventhandler_macos.cc
index 8066acb24f9da936b306382fd265eecdd29708e5..ed66bfc443e677809cb26efc9ca8fe10e95445f3 100644
--- a/dart/runtime/bin/eventhandler_macos.cc
+++ b/dart/runtime/bin/eventhandler_macos.cc
@@ -136,7 +136,8 @@ EventHandlerImplementation::~EventHandlerImplementation() {
 }
 
 
-SocketData* EventHandlerImplementation::GetSocketData(intptr_t fd) {
+SocketData* EventHandlerImplementation::GetSocketData(intptr_t fd,
+                                                      bool is_listening) {
   ASSERT(fd >= 0);
   HashMap::Entry* entry = socket_map_.Lookup(
       GetHashmapKeyFromFd(fd), GetHashmapHashFromFd(fd), true);
@@ -145,7 +146,7 @@ SocketData* EventHandlerImplementation::GetSocketData(intptr_t fd) {
   if (sd == NULL) {
     // If there is no data in the hash map for this file descriptor a
     // new SocketData for the file descriptor is inserted.
-    sd = new SocketData(fd);
+    sd = new SocketData(fd, is_listening);
     entry->value = sd;
   }
   ASSERT(fd == sd->fd());
@@ -185,7 +186,8 @@ void EventHandlerImplementation::HandleInterruptFd() {
     } else if (msg[i].id == kShutdownId) {
       shutdown_ = true;
     } else {
-      SocketData* sd = GetSocketData(msg[i].id);
+      SocketData* sd = GetSocketData(
+          msg[i].id, (msg[i].data & (1 << kListeningSocket)) != 0);
       if (IS_COMMAND(msg[i].data, kShutdownReadCommand)) {
         // Close the socket for reading.
         shutdown(sd->fd(), SHUT_RD);
@@ -207,14 +209,17 @@ void EventHandlerImplementation::HandleInterruptFd() {
             AddToKqueue(kqueue_fd_, sd);
           }
         }
-      } else {
-        ASSERT_NO_COMMAND(msg[i].data);
+      } else if (IS_COMMAND(msg[i].data, kSetEventMaskCommand)) {
+        // `events` can only have kInEvent/kOutEvent flags set.
+        intptr_t events = msg[i].data & EVENT_MASK;
+        ASSERT(0 == (events & ~(1 << kInEvent) & ~(1 << kOutEvent)));
+
         // Setup events to wait for.
-        ASSERT((msg[i].data > 0) && (msg[i].data < kIntptrMax));
         ASSERT(sd->port() == 0);
-        sd->SetPortAndMask(msg[i].dart_port,
-                           static_cast<intptr_t>(msg[i].data));
+        sd->SetPortAndMask(msg[i].dart_port, events);
         AddToKqueue(kqueue_fd_, sd);
+      } else {
+        UNREACHABLE();
       }
     }
   }