blink::LocalFrame

the document host and local‑root boundary.
The local frame owns the Document and its LocalFrameView. The local root frame coordinates lifecycle for its subtree (including OOPIF boundaries handled later on the viz side). (Chromium Git Repositories)

Key methods/fields

* bool IsLocalRoot() const; LocalFrame& LocalFrameRoot() const; — define the subtree that this frame is responsible for during lifecycle (important for scoping style/layout/paint). (Chromium Git Repositories)

* Accessors into the view and document (used throughout the lifecycle calls). (Chromium Git Repositories)

Hands off to: LocalFrameView (view/lifecycle engine) and Document.