These sources provide an extensive architectural overview of the core C++ classes that implement Chromium's input handling, synchronization, and animation systems. The documents detail the multi-process, multi-threaded journey of user input, beginning at the operating system and progressing through the Browser process (using classes like DesktopWindowTreeHost and RenderWidgetHost) and into the Renderer process. A major theme is the mechanism for offloading work from the main thread to the dedicated compositor thread, utilizing a dual-tree architecture where objects like cc::Layer and cc::LayerImpl are synchronized via the critical commit process. Finally, the text explains the dedicated animation framework, which uses a PushPropertiesTo synchronization pattern to ensure smooth, main-thread-independent motion controlled by the AnimationHost and KeyframeModel classes.