Add UMA to track the number of live URLRequests.

net/log/net_log_util.cc

Index: net/log/net_log_util.cc
diff --git a/net/log/net_log_util.cc b/net/log/net_log_util.cc
index 2d1b2dcc9f70868a8463aa6cd081a5675e9a7fe6..85b546043c83bb470774f0730564c88eae2fe443 100644
--- a/net/log/net_log_util.cc
+++ b/net/log/net_log_util.cc
@@ -515,7 +515,7 @@ NET_EXPORT void CreateNetLogEntriesForActiveObjects(
     DCHECK(context->CalledOnValidThread());
     // Contexts should all be using the same NetLog.
     DCHECK_EQ((*contexts.begin())->net_log(), context->net_log());
-    for (auto* request : *context->url_requests()) {
+    for (auto* request : context->url_requests()) {
       requests.push_back(request);
     }
   }