Progress
...
indicator and growlers
Summary
For slow to load pages (e.g., Forecasts in RAFT) we’ve built in a progress indicator to show users that the page is loading.
...
Example (in use, with an interaction, in context)
Example 
Related patterns
Problem
Users need to see that the requested action (for instance, opening a large workset) is in progress.
Users are working on a long scrolling page and may not notice calculations or other changes happening at the top of the screen when they click the Save button lower on the screen.
...