Drive-by: Use perfect forwarding for AddTraceEvent arguments.

BUG=406277

Committed: https://crrev.com/dcac49af485fe5d4c0027f153901435dbb29c232
Review-Url: https://codereview.chromium.org/2367603002
Cr-Original-Commit-Position: refs/heads/master@{#39742}
Cr-Commit-Position: refs/heads/master@{#39789}