Zooming in Fennec since bug 576192 works only in remote tabs, and does not work for local tabs such as about:home, about:firstrun. (Note: changing the scale was temporily disabled in the local browser binding because it did not work and caused problems with clicking; see bug 596824.)

We could probably do this with CSS transforms for b2, but it would be a short-term throwaway hack. Long term, we need to implement the same API that we use for remote browsers (bug 593168); cjones is working on this. For b2 I suggest leaving the current code in place to lock the viewport for all local tabs.

Chris - should we just kill this bug and focus on bug 593168?

Well, depends on what you want this bug to cover. Bug 593168 isn't going to make b2, so if zooming local tabs blocks b2, we'll need the CSS transform hacks. If zooming local tabs doesn't block, then this bug can cover the frontend changes to use bug 593168 (if any).

Oh, and I now see that this is blocking b3, so only the last sentence above applies.

This is sort of covered by https://litmus.mozilla.org/show_test.cgi?id=12336 , since with the first launch of Fennec, the about:home page is loaded by default.

We don't have any about pages that warrant zooming. When we do, we can open a specific bug.