Refactor the io resource classes

sdk/lib/io/io_resource_info.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 part of dart.io;
 
 abstract class _IOResourceInfo {
   final String type;
   final int id;
   String get name;
@@ skipping 13 matching lines @@
       {
         // The type for a reference object is prefixed with @ in observatory.
         'type': '@$type',
         'id': id,
         'name': name,
       };
 
   static int getNextID() => _count++;
 }
 
-// TODO(ricow): Move stopwatch into this class and use it for both files
-// and sockets (by using setters on totalRead/totalWritten). Also, consider
-// setting readCount and writeCount in those setters.
 abstract class _ReadWriteResourceInfo extends _IOResourceInfo {
   int totalRead;
   int totalWritten;
   int readCount;
   int writeCount;
   double lastRead;
   double lastWrite;
 
+  static final Stopwatch _sw = new Stopwatch()..start();
+  static double get timestamp => _sw.elapsedMicroseconds / 1000000.0;
+
+  // Not all call sites use this. In some cases, e.g., a socket, a read does
+  // not always mean that we actually read some bytes (we may do a read to see
+  // if there are some bytes available).
+  void addRead(int bytes) {
+    totalRead += bytes;
+    readCount++;
+    lastRead = timestamp;
+  }
+
+  // In cases where we read but did not neccesarily get any bytes, use this to
+  // update the readCount and timestamp. Manually update totalRead if any bytes
+  // where acutally read.
+  void didRead() => addRead(0);
+
+  void addWrite(int bytes) {
+    totalWritten += bytes;
+    writeCount++;
+    lastWrite = timestamp;
+  }
+
   _ReadWriteResourceInfo(String type) :
     totalRead = 0,
     totalWritten = 0,
     readCount = 0,
     writeCount = 0,
     lastRead = 0.0,
     lastWrite = 0.0,
     super(type);
 
   Map<String, String> get fullValueMap =>
@@ skipping 141 matching lines @@
     assert(!openSockets.containsKey(info.id));
     openSockets[info.id] = info;
   }
 
   static SocketClosed(_SocketResourceInfo info) {
     assert(openSockets.containsKey(info.id));
     openSockets.remove(info.id);
   }
 
 }