This directory contains the service-side implementation of the Compute Pressure API.
The system is made up of the following components.
device::mojom::PressureManager, defined in services, is the interface implemented in the browser side (content::PressureServiceImpl) to communicate with the renderer and implemented in services (device::PressureManagerImpl) to communicate with the browser side.
device::PressureManagerImpl is the top-level class for the services side implementation. The class is responsible for handling the communication between the browser and services sides.
device::mojom::PressureClient is the interface that client of the device::mojom::PressureManager interface must implement to receive device::mojom::PressureUpdate.
device::mojom::PressureUpdate represents the device's compute pressure update, composed of the device::mojom::PressureState and the timestamp. This information is collected by device::CpuProbe and bubbled up by device::PlatformCollector to device::PressureManagerImpl, which broadcasts the information to the content::PressureClientImpl instances first and then to blink::PressureClientImpl instances.
device::CpuProbe is an abstract base class that drives measuring the device‘s compute pressure state from the operating system. The class is responsible for invoking platform-specific measurement code at regular intervals, and for straddling between sequences to meet the platform-specific code’s requirements. This interface is also a dependency injection point for tests.
content::PressureService* is the bridge between the renderer and the services sides. This class maintains content::PressureClientImpl instances per source type.
content::PressureClientImpl implements the device::mojom::PressureClient interface to receive device::mojom::PressureUpdate from device::PressureManagerImpl instance and broadcasts the information to the blink::PressureClientImpl instance.
blink::PressureObserver implements bindings for the PressureObserver interface. There can be more than one PressureObserver per frame.
blink::PressureObserverManager keeps track of blink::PressureClientImpl and the connection to the content::PressureService* instance. The class is responsible for handling the communication between the renderer and browser sides.
blink::PressureClientImpl implements the device::mojom::PressureClient interface to receive device::mojom::PressureUpdate from content::PressureClientImpl and broadcasts the information to active blink::PressureObserver. This class also keeps track of State and active blink::PressureObserver per source type.