Android: disables observing changes for font prefs.

On Android, there's no exposed way to change font preferences.
This will save ~200KB of heap.
This change was done in crrev.com/12529014 but was later reverted in
crrev.com/444843002 by mistake. So, remove them again.

BUG=716195

Review-Url: https://codereview.chromium.org/2850503006
Cr-Commit-Position: refs/heads/master@{#468717}
1 file changed