message: stream_info: add response_flags mocks
diff: using testing::_;
  using testing::Const;
  using testing::Invoke;
  +using testing::Return;
  using testing::ReturnPointee;
  using testing::ReturnRef;
  @@ -96,6 +97,13 @@ MockStreamInfo::MockStreamInfo()
  ON_CALL(*this, hasResponseFlag(_)).WillByDefault(Invoke([this](ResponseFlag flag) {
  return response_flags_ & flag;
  }));
  + ON_CALL(*this, intersectResponseFlags(_)).WillByDefault(Invoke([this](uint64_t response_flags) {
  + return (response_flags_ & response_flags) != 0;
  + }));
  + ON_CALL(*this, hasAnyResponseFlag()).WillByDefault(Invoke([this]() {
  + return response_flags_ != 0;
  + }));
  + ON_CALL(*this, responseFlags()).WillByDefault(Return(response_flags_));
  ON_CALL(*this, upstreamHost()).WillByDefault(ReturnPointee(&host_));
  ON_CALL(*this, dynamicMetadata()).WillByDefault(ReturnRef(metadata_));
  