Add missing <functional> and <vector> includes

Bug: 175635923
Test: m MODULES-IN-system-core-libutils
Change-Id: I065907a58a88723ae512f155dfde2d2fcb3fc322
diff --git a/libutils/String16_fuzz.cpp b/libutils/String16_fuzz.cpp
index a271aee..8f9781b 100644
--- a/libutils/String16_fuzz.cpp
+++ b/libutils/String16_fuzz.cpp
@@ -13,7 +13,9 @@
  * See the License for the specific language governing permissions and
  * limitations under the License.
  */
+#include <functional>
 #include <iostream>
+#include <vector>
 
 #include "fuzzer/FuzzedDataProvider.h"
 #include "utils/String16.h"