Costumes and Sounds tabs are too wide on tablets

[chrisgarrity]

Expected Behavior

All of the editor interface should be visible.

Actual Behavior

This occurs on any device with a browser viewport that is exactly the minimum required 1024x768. That includes iPads, and many Android tablets. You can simulate it by resizing your browser window to that size.

When switching between the code, costumes and sounds tags on an iPad mini, the paint and sound editors are wider than the default code workspace and the stage and sprite info areas get pushed to the right. This ends up cutting off part of the interface. Here's the costumes tab on an iPad

Here's the sounds tab in Mac Chrome with a 1024x768 window, note that the add backdrop and fullscreen buttons are gone:

Steps to Reproduce

Edit a project on an iPad mini or any configuration where the window is 1024x768

Operating System and Browser

Several