Use hash map for event handler file descriptor map

runtime/platform/utils.cc

 // Copyright (c) 2012, 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.
 
 #include "platform/utils.h"
 
 namespace dart {
 
 // Implementation is from "Hacker's Delight" by Henry S. Warren, Jr.,
 // figure 3-3, page 48, where the function is called clp2.
@@ skipping 57 matching lines @@
 
   // Do a few final mixes of the hash to ensure the last few bytes are
   // well-incorporated.
   hash ^= hash >> 13;
   hash *= M;
   hash ^= hash >> 15;
   return hash;
 }
 
 
-uint32_t WordHash(word key) {
+uint32_t Utils::WordHash(word key) {
   // TODO(iposva): Need to check hash spreading.
   // This example is from http://www.concentric.net/~Ttwang/tech/inthash.htm
   uword a = static_cast<uword>(key);
   a = (a + 0x7ed55d16) + (a << 12);
   a = (a ^ 0xc761c23c) ^ (a >> 19);
   a = (a + 0x165667b1) + (a << 5);
   a = (a + 0xd3a2646c) ^ (a << 9);
   a = (a + 0xfd7046c5) + (a << 3);
   a = (a ^ 0xb55a4f09) ^ (a >> 16);
   return static_cast<uint32_t>(a);
 }
 
 }  // namespace dart