Add 'Clear' method to HashMap/HashSet templates.

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>
@@ skipping 227 matching lines @@
   for (int i = 0; i < 2; ++i) {
     for (char ch = 'a'; ch <= 'z'; ++ch) {
       std::string key('z' - ch + 1, ch);
       expected.insert(key);
       bool present = actual.Insert(String::Handle(String::New(key.c_str())));
       EXPECT_EQ((i != 0), present);
       Validate(actual);
       VerifyStringSetsEqual(expected, actual, ordered);
     }
   }
-  // TODO(koda): Delete all entries.
+  actual.Clear();
+  EXPECT_EQ(0, actual.NumOccupied());
   actual.Release();
 }
 
 
 template<typename Map>
 void TestMap(intptr_t initial_capacity, bool ordered) {
   std::map<std::string, int> expected;
   Map actual(HashTables::New<Map>(initial_capacity));
   // Insert the following (strings, int) mapping:
   // aaa...aaa -> 26
   // bbb..bbb -> 25
   // ...
   // yy -> 2
   // z -> 1
   for (int i = 0; i < 2; ++i) {
     for (char ch = 'a'; ch <= 'z'; ++ch) {
       int length = 'z' - ch + 1;
       std::string key(length, ch);
       // Map everything to zero initially, then update to their final values.
       int value = length * i;
       expected[key] = value;
       bool present =
           actual.UpdateOrInsert(String::Handle(String::New(key.c_str())),
                                 Smi::Handle(Smi::New(value)));
       EXPECT_EQ((i != 0), present);
       Validate(actual);
       VerifyStringMapsEqual(expected, actual, ordered);
     }
   }
-  // TODO(koda): Delete all entries.
+  actual.Clear();
+  EXPECT_EQ(0, actual.NumOccupied());
   actual.Release();
 }
 
 
 TEST_CASE(Sets) {
   for (intptr_t initial_capacity = 0;
        initial_capacity < 32;
        ++initial_capacity) {
     TestSet<UnorderedHashSet<TestTraits> >(initial_capacity, false);
     TestSet<EnumIndexHashSet<TestTraits> >(initial_capacity, true);
   }
 }
 
 
 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