Add usage and collision details to the hash table data structure in order to determine effectivenes…

runtime/vm/hash_table_test.cc

 // Copyright (c) 2014, 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 <algorithm>
 #include <cstring>
 #include <map>
 #include <set>
 #include <string>
 #include <utility>
 #include <vector>
 
 #include "platform/assert.h"
 #include "vm/unit_test.h"
 #include "vm/hash_table.h"
 
 namespace dart {
 
 // Various ways to look up strings. Uses length as the hash code to make it
 // easy to engineer collisions.
 class TestTraits {
  public:
   static const char* Name() { return "TestTraits"; }
+  static bool ReportStats() { return false; }
 
   static bool IsMatch(const char* key, const Object& obj) {
     return String::Cast(obj).Equals(key);
   }
   static uword Hash(const char* key) {
     return static_cast<uword>(strlen(key));
   }
   static bool IsMatch(const Object& a, const Object& b) {
     return a.IsString() && b.IsString() &&
         String::Cast(a).Equals(String::Cast(b));
@@ skipping 263 matching lines @@
 TEST_CASE(Maps) {
   for (intptr_t initial_capacity = 0;
        initial_capacity < 32;
        ++initial_capacity) {
     TestMap<UnorderedHashMap<TestTraits> >(initial_capacity, false);
     TestMap<EnumIndexHashMap<TestTraits> >(initial_capacity, true);
   }
 }
 
 }  // namespace dart