IWYU: add includes for uint64_t and std::string

Bug: 819294
Change-Id: Iae844f8b6cf6bba879cb320c95ebf88f65e1385f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2273161Reviewed-by: Yao Xiao <yaoxia@chromium.org>
Commit-Queue: Yao Xiao <yaoxia@chromium.org>
Cr-Commit-Position: refs/heads/master@{#783978}

components/federated_learning/sim_hash.h

@@ -5,7 +5,9 @@
 #ifndef COMPONENTS_FEDERATED_LEARNING_SIM_HASH_H_
 #define COMPONENTS_FEDERATED_LEARNING_SIM_HASH_H_
 
+#include <stdint.h>
 #include <set>
+#include <string>
 #include <unordered_set>
 
 namespace federated_learning {