Move duplicate code to RendererClientBase::ShouldLoadPreload helper

Editor assessment

A tidy, self-sufficient refactor header: imperative, lowercase, and precise — naming the new `RendererClientBase::ShouldLoadPreload` helper tells reviewers exactly where to look. At about 77 characters it runs past the 72-char guideline, though the specificity arguably justifies it. The missing piece is a one-line body explaining the motivation: deduplication ahead of an upcoming change, or pure cleanup? For a localized refactor this omission is tolerable, and the type is certainly right since no behavior change is implied. A scope would have grouped it nicely in generated changelogs.