Simplify VirtualMemory by removing unused ReserveAligned method.

runtime/vm/virtual_memory_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 "platform/assert.h"
 #include "vm/unit_test.h"
 #include "vm/virtual_memory.h"
 
 namespace dart {
 
@@ skipping 19 matching lines @@
   char* buf = reinterpret_cast<char*>(vm->address());
   buf[0] = 'a';
   buf[1] = 'c';
   buf[2] = '/';
   buf[3] = 'd';
   buf[4] = 'c';
   buf[5] = 0;
   EXPECT_STREQ("ac/dc", buf);
 
   delete vm;
-
-  const intptr_t kAlignment = 1 * MB;
-  vm = VirtualMemory::ReserveAligned(kVirtualMemoryBlockSize, kAlignment);
-  ASSERT((vm->start() & (kAlignment - 1)) == 0);
-  delete vm;
 }
 
 }  // namespace dart