Switch to standard integer types in components/, part 1 of 4.

BUG=138542
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Review URL: https://codereview.chromium.org/1546143002

Cr-Commit-Position: refs/heads/master@{#366873}
diff --git a/components/drive/file_system/search_operation_unittest.cc b/components/drive/file_system/search_operation_unittest.cc
index 83ab746..474c7df 100644
--- a/components/drive/file_system/search_operation_unittest.cc
+++ b/components/drive/file_system/search_operation_unittest.cc
@@ -4,6 +4,8 @@
 
 #include "components/drive/file_system/search_operation.h"
 
+#include <stddef.h>
+
 #include "base/callback_helpers.h"
 #include "components/drive/change_list_loader.h"
 #include "components/drive/file_system/operation_test_base.h"