message: Fix the build error of implicit conversion from absl::string_view to std::string.
diff: @@ -77,10 +77,10 @@ class SingleKanjiRewriterTest : public ::testing::Test {
  Segment::Candidate *candidate = segment->add_candidate();
  candidate->Init();
  - candidate->key = key;
  - candidate->content_key = key;
  - candidate->value = value;
  - candidate->content_value = value;
  + candidate->key.assign(key.data(), key.size());
  + candidate->content_key.assign(key.data(), key.size());
  + candidate->value.assign(value.data(), value.size());
  + candidate->content_value.assign(value.data(), value.size());
  }
  static bool Contains(const Segments &segments, absl::string_view word) {
  