Google Chrome	71.0.3578.98 (Official Build) (64-bit)
Revision	15234034d19b85dcd9a03b164ae89d04145d8368-refs/branch-heads/3578@{#897}
OS	Mac OS X

What steps will reproduce the problem?
(1) Open the dev tools network panel.
(2) Load a page with a bunch of script files.

What is the expected result?

Doesn't download source maps until I go to the Sources panel, and only downloads the map for the files I look at.

What happens instead?

Eagerly downloads the source maps for every file while the page is loading which means the network is full of map requests which changes how the network timeline looks.

It also looks like these source map requests don't show up in the network timeline which is confusing since we see our express server getting flooded with map requests but Chrome doesn't show them.