The cc scheduler attempts to provide the main and impl thread the same rate as the BeginFrameSource, which means for the Blimp compositor, actively dynamic pages show a high frequency of updates from the engine to the client adding to the data use.
(See https://docs.google.com/document/d/15GLhtmiZj5QzaD2x3iHNF9-42pdxbvAvg9VVxxlot2Q)

This requires the scheduler to throttle commits initiated from the engine and pause them after a period of user activity. Making these decisions needs plumbing of information about why a commit is necessary to the Scheduler to allow different policies for throttling them.