Include <memory> in lock_free_address_hash_set_unittest.cc

This fixes a compiler error.

../../base/sampling_heap_profiler/lock_free_address_hash_set_unittest.cc(148,22):  error: no member named 'make_unique' in namespace 'std'
  auto thread = std::make_unique<WriterThread>(&set, &cancel);
                ~~~~~^
../../base/sampling_heap_profiler/lock_free_address_hash_set_unittest.cc(148,34):  error: 'WriterThread' does not refer to a value
  auto thread = std::make_unique<WriterThread>(&set, &cancel);
                                 ^
../../base/sampling_heap_profiler/lock_free_address_hash_set_unittest.cc(116,7):  note: declared here
class WriterThread : public SimpleThread {
      ^
../../base/sampling_heap_profiler/lock_free_address_hash_set_unittest.cc(148,48):  error: expression result unused [-Werror,-Wunused-value]
  auto thread = std::make_unique<WriterThread>(&set, &cancel);
                                               ^~~~
3 errors generated.

ninja: build stopped: subcommand failed.
Change-Id: I72d5bddf448c091417f9497b6cb751df5a75dff1
Reviewed-on: https://chromium-review.googlesource.com/1129759Reviewed-by: Alexei Filippov <alph@chromium.org>
Commit-Queue: Alexei Filippov <alph@chromium.org>
Cr-Commit-Position: refs/heads/master@{#573513}

base/sampling_heap_profiler/lock_free_address_hash_set_unittest.cc

@@ -6,6 +6,7 @@
 
 #include <stdlib.h>
 #include <cinttypes>
+#include <memory>
 
 #include "base/allocator/allocator_shim.h"
 #include "base/debug/alias.h"