The provided source offers an extensive architectural analysis of Chromium’s cc::CommitState struct, detailing its critical function as the intermediary data structure that facilitates communication between the main rendering thread and the compositor (impl) thread during frame commits. The core purpose of CommitState is to take a snapshot of the main thread’s compositor state, enabling non-blocking commits by transferring all necessary persistent settings and one-time updates, like resource requests and animation data, in a single package. The document breaks down the structure into persistent fields (settings that carry over between frames) and ephemeral fields (one-time updates that are consumed and cleared after the commit), distinguishing it from the ThreadUnsafeCommitState, which holds non-copyable pointers that require thread synchronization. This design is crucial for performance and safety, as it batches updates and minimizes the duration the main thread must stall during the commitment phase of the rendering pipeline.