UserAgent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/60.0.3112.101 Safari/537.36

Steps to reproduce the problem:
1. go to https://www.webcomponents.org/element/PolymerElements/paper-button/demo/demo/index.html
2. right click on one of the paper-buttons and inspect it, and look at the 'styles' tab on the 'elements' tab
3. try to view the 'sizes' box (not sure what it's called) at the bottom of that panel
4. change the dev tools layout, eg, if viewing with the tools in the same window, on the right, move the splitter so that the size of the dev tools is small...this cause a different layout.

What is the expected behavior?
I expect to be able to see that quickly.

What went wrong?
I have to scroll because all the custom properties are listed and there are many many many of them, and no way to 'collapse' them.

Did this work before? N/A 

Chrome version: 60.0.3112.101  Channel: stable
OS Version: 10.0
Flash Version: 

I suggest that the sizes box is at the top, and/or each block of rules is collapsible and collapsed by default; or perhaps they're individually scrollable...something like that...or perhaps the sizes box could be its own tab (a bit like when the dev tools are vertically narrow).