Responsive navigation menu doesn't collapse in iPad in portrait mode

Bug 1308857. The problem appears to be that the collapse logic is based
around a <= and a >=, and the iPad in portrait mode falls right in the middle
so it triggers both. Changing this to a more logical <= and > pair fixes things.

Change-Id: Iacb8d53daff0f06a6f414bf5e4aafdee1337dfa3