Use in-class initializers for base::WeakPtrFactory in net/.

Generated by: https://chromium-review.googlesource.com/c/chromium/src/+/1689216

Bug: 981415
Change-Id: I8b3e41ce53df33f8fc201e175a65cae3a9e07669
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1691082
Reviewed-by: Eric Roman <[email protected]>
Commit-Queue: Jeremy Roman <[email protected]>
Cr-Commit-Position: refs/heads/master@{#675307}
diff --git a/net/dns/host_resolver_mdns_task.cc b/net/dns/host_resolver_mdns_task.cc
index cc5c364..356278b5 100644
--- a/net/dns/host_resolver_mdns_task.cc
+++ b/net/dns/host_resolver_mdns_task.cc
@@ -128,7 +128,7 @@
     MDnsClient* mdns_client,
     const std::string& hostname,
     const std::vector<DnsQueryType>& query_types)
-    : mdns_client_(mdns_client), hostname_(hostname), weak_ptr_factory_(this) {
+    : mdns_client_(mdns_client), hostname_(hostname) {
   DCHECK(!query_types.empty());
   for (DnsQueryType query_type : query_types) {
     transactions_.emplace_back(query_type, this);