--- a/devtools/client/responsive.html/index.js
+++ b/devtools/client/responsive.html/index.js
@@ -94,16 +94,19 @@ window.dispatch = action => bootstrap.di
 Object.defineProperty(window, "store", {
   get: () => bootstrap.store,
   enumerable: true,
 });
 
 // Dispatch a `changeDisplayPixelRatio` action when the browser's pixel ratio is changing.
 // This is usually triggered when the user changes the monitor resolution, or when the
 // browser's window is dragged to a different display with a different pixel ratio.
+// TODO: It would be better to move this watching into the actor, so that it can be
+// better synchronized with any overrides that might be applied.  Also, reading a single
+// value like this makes less sense with multiple viewports.
 function onDPRChange() {
   let dpr = window.devicePixelRatio;
   let mql = window.matchMedia(`(resolution: ${dpr}dppx)`);
 
   function listener() {
     bootstrap.dispatch(changeDisplayPixelRatio(window.devicePixelRatio));
     mql.removeListener(listener);
     onDPRChange();