Edit module's JS gets loaded even on admin pages

This is due to the changes introduced by effulgentsia at #1824500-78: In-place editing for Fields:

Similarly, I didn't see why the path_is_admin() check was needed any more: it used to be in earlier versions of this patch, but I think the JS code has become more robust since then, as David points out in 71.4.

In #1824500-71: In-place editing for Fields, point 4, David_Rothstein pointed out:

+/**
+ * Implements hook_toolbar().
+ */
+function edit_toolbar() {
+  if (path_is_admin(current_path())) {
+    return;
+  }

Why? The "Edit" link already hides itself if there isn't any editable content on the page, right? (Many admin pages will tend to fall under that rule anyway, but for ones that aren't I don't see why inline editing should be prevented.)

I'm not sure how I missed it in that issue, but:

• It's correct that the "Edit" tab doesn't show up unless there's something in-place editable on the current page, so we indeed don't need to do explicitly prevent Edit from loading on admin/* pages.
• The downside: we're now loading Edit's JS on *all* pages (provided the current user has the access in-place editing permission). That's a lot of page weight where that doesn't need to be. This is bad for performance.

The real question here is: can we think of a use case for in-place editing on admin/* pages and if so, what is that use case? If we can't, we should explicitly prevent Edit's JS from loading on admin pages.