browser: enforcing a min-width on the sidebar after which content don't wrap anymore. width < 250 squishes content too much for it to be readable.
browser: enforcing a min-width on the sidebar after which content
don't wrap anymore. width < 250 squishes content too much for it
to be readable.

Change-Id: I343bb069c781013df535837dc86e4eb3052e7011

vanadium/browser,vanadium/browser,vanadium/browser,vanadium/browser