Bug 710298 provides a preference, browser.zoom.reflowOnZoom, that allows users to enable a feature that constrains the max line box width after zooming in to a page. This feature is part of readability 2.0. We should provide a front-end so that nightly testers can more easily enable this feature and play with it, but it should be OFF by default.
Created attachment 667109 [details] [diff] [review] b795932
Inbound, with changes requested by blassey: https://hg.mozilla.org/integration/mozilla-inbound/rev/b83159dadf3c
"Reflow-On-Zoom" option was added in Setting and it's disabled by default on the latest Nightly. Closing bug as verified fixed on: Firefox 18.0a1 (2012-10-09) Device: Galaxy Note OS: Android 4.0.4