The page load metrics subsystem captures and records UMA metrics related to page loading. This includes page timing metrics, such as time to first paint, as well as page interaction metrics, such as number of page loads aborted before first paint.

The page load metrics subsystem is shared by Chrome and WebView, but not supported on iOS, as it requires hooks into Blink for page timing metrics that are unavailable on iOS.

This component has the following structure:

• components/page_load_metrics/browser: browser process code
• components/page_load_metrics/common/: code shared by browser and renderer, such as IPC messages
• components/page_load_metrics/renderer : renderer process code

For additional information on this subsystem, see https://docs.google.com/document/d/1HJsJ5W2H_3qRdqPAUgAEo10AF8gXPTXZLUET4X4_sII/edit