The source provides a detailed technical exploration of SyncedProperty, a critical synchronization mechanism within Chromium's compositor (cc) designed to manage properties updated concurrently on both the main (Blink) and compositor (impl) threads. Its primary function is to resolve conflicts and prevent lost updates for properties like scroll offsets and page scale factor by treating changes as mathematical deltas (additive for offsets, multiplicative for scale) that are merged rather than overwritten. The text outlines the life cycle and key methods of SyncedProperty (such as PushMainToPending and PullDeltaForMainThread), explaining how it facilitates smooth, non-blocking updates on the compositor while ensuring the main thread eventually reflects these changes. Furthermore, the source differentiates SyncedProperty usage from other compositor animations (like transforms and opacity), clarifies its interaction with property trees and the frame commitment pipeline, and touches upon its role in multi-process communication, especially regarding browser UI elements like the top controls offset.
