Only return eventhandler tokens in stacks of 8, to avoid runtime calls.

runtime/bin/eventhandler_linux.h

Index: runtime/bin/eventhandler_linux.h
diff --git a/runtime/bin/eventhandler_linux.h b/runtime/bin/eventhandler_linux.h
index 54f02509531446572bf84b1e489df896cc95b19c..f6f3f9a2ac6f3885e76cbfee8c0f2b379778b8a6 100644
--- a/runtime/bin/eventhandler_linux.h
+++ b/runtime/bin/eventhandler_linux.h
@@ -31,7 +31,7 @@ class InterruptMessage {
 
 class SocketData {
  public:
-  explicit SocketData(intptr_t fd) : fd_(fd), port_(0), mask_(0), tokens_(8) {
+  explicit SocketData(intptr_t fd) : fd_(fd), port_(0), mask_(0), tokens_(16) {
     ASSERT(fd_ != -1);
   }
 
@@ -53,6 +53,8 @@ class SocketData {
   intptr_t fd() { return fd_; }
   Dart_Port port() { return port_; }
 
+  bool IsListeningSocket() { return (mask_ & (1 << kListeningSocket)) != 0; }
+
   // Returns true if the last token was taken.
   bool TakeToken() {
     ASSERT(tokens_ > 0);