Add Dart_Allocate to the C++ API

runtime/vm/dart_api_impl_test.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 "bin/builtin.h"
 #include "include/dart_api.h"
 #include "include/dart_mirrors_api.h"
 #include "include/dart_native_api.h"
 #include "platform/assert.h"
 #include "platform/json.h"
@@ skipping 3901 matching lines @@
   Dart_Handle result = Dart_New(cls, Dart_Null(), 0, NULL);
   EXPECT_VALID(result);
   bool instanceof = false;
   EXPECT_VALID(Dart_ObjectIsType(result, cls, &instanceof));
   EXPECT(instanceof);
   int64_t int_value = 0;
   Dart_Handle foo = Dart_GetField(result, NewString("foo"));
   EXPECT_VALID(Dart_IntegerToInt64(foo, &int_value));
   EXPECT_EQ(7, int_value);
 
+  // Allocate without a constructor.
+  result = Dart_Allocate(cls);

[siva, 2013/06/19 15:36:24]

I think you may run into conflicts with my CL. I have changed this
test to do a Dart_GetType above so that it uses type objects.

If you submit first I will resolve this conflict otherwise you may have to
resolve it.

+  EXPECT_VALID(result);
+  instanceof = false;
+  EXPECT_VALID(Dart_ObjectIsType(result, cls, &instanceof));
+  EXPECT(instanceof);
+  foo = Dart_GetField(result, NewString("foo"));
+  EXPECT(Dart_IsNull(foo));
+
   // Invoke the unnamed constructor with an empty string.
   result = Dart_New(cls, NewString(""), 0, NULL);
   EXPECT_VALID(result);
   instanceof = false;
   EXPECT_VALID(Dart_ObjectIsType(result, cls, &instanceof));
   EXPECT(instanceof);
   int_value = 0;
   foo = Dart_GetField(result, NewString("foo"));
   EXPECT_VALID(Dart_IntegerToInt64(foo, &int_value));
   EXPECT_EQ(7, int_value);
@@ skipping 4167 matching lines @@
                                    NewString("main"),
                                    0,
                                    NULL);
   int64_t value = 0;
   result = Dart_IntegerToInt64(result, &value);
   EXPECT_VALID(result);
   EXPECT_EQ(8, value);
 }
 
 }  // namespace dart