Make the event-handler handle backpreasure.

runtime/bin/eventhandler_android.h

Index: runtime/bin/eventhandler_android.h
diff --git a/runtime/bin/eventhandler_android.h b/runtime/bin/eventhandler_android.h
index 5a80eef414209e27435277427740ad9f92975a48..2647164fbf31d90782a4cf978157dd85eb5548c4 100644
--- a/runtime/bin/eventhandler_android.h
+++ b/runtime/bin/eventhandler_android.h
@@ -31,17 +31,11 @@ class InterruptMessage {
 class SocketData {
  public:
   explicit SocketData(intptr_t fd)
-      : tracked_by_epoll_(false), fd_(fd), port_(0), mask_(0) {
+      : fd_(fd), port_(0), mask_(0), tokens_(8) {
     ASSERT(fd_ != -1);
   }
 
-  void ShutdownRead() {
-    shutdown(fd_, SHUT_RD);
-  }
-
-  void ShutdownWrite() {
-    shutdown(fd_, SHUT_WR);
-  }
+  intptr_t GetPollEvents();
 
   void Close() {
     port_ = 0;
@@ -50,9 +44,6 @@ class SocketData {
     fd_ = -1;
   }
 
-  bool IsListeningSocket() { return (mask_ & (1 << kListeningSocket)) != 0; }
-  bool IsPipe() { return (mask_ & (1 << kPipe)) != 0; }
-
   void SetPortAndMask(Dart_Port port, intptr_t mask) {
     ASSERT(fd_ != -1);
     port_ = port;
@@ -61,15 +52,26 @@ class SocketData {
 
   intptr_t fd() { return fd_; }
   Dart_Port port() { return port_; }
-  intptr_t mask() { return mask_; }
-  bool tracked_by_epoll() { return tracked_by_epoll_; }
-  void set_tracked_by_epoll(bool value) { tracked_by_epoll_ = value; }
+
+  // Returns true if the last token was taken.
+  bool TakeToken() {
+    ASSERT(tokens_ > 0);
+    tokens_--;
+    return tokens_ == 0;
+  }
+
+  // Returns true if the tokens was 0 before adding.
+  bool ReturnToken() {
+    ASSERT(tokens_ >= 0);
+    tokens_++;
+    return tokens_ == 1;
+  }
 
  private:
-  bool tracked_by_epoll_;
   intptr_t fd_;
   Dart_Port port_;
   intptr_t mask_;
+  int tokens_;
 };
 
 
@@ -80,8 +82,8 @@ class EventHandlerImplementation {
 
   // Gets the socket data structure for a given file
   // descriptor. Creates a new one if one is not found.
-  SocketData* GetSocketData(intptr_t fd, bool* is_new);
-  void Notify(intptr_t id, Dart_Port dart_port, intptr_t data);
+  SocketData* GetSocketData(intptr_t fd);
+  void SendData(intptr_t id, Dart_Port dart_port, intptr_t data);
   void Start(EventHandler* handler);
   void Shutdown();