48.0 includes a change to the update URL that allows us to detect CPU features (see bug 1271761). We need to create a watershed rule to route all Windows users through 48.0 to make sure we can detect their CPU features before offering them 49.0 (or a deprecation notice).

This watershed is setup for pointing at 48 -- using the same rate as was requested already.

Was able to confirm the 48.0 watershed when running ondemand update tests for 48.0.1 on release-localtest [1], and release-cdntest [2]. The watershed was bumped to 48.0.1 when we released officially so tests on the release channel [3] have passed as expected for versions <48.0.1. [1] - https://treeherder.mozilla.org/#/jobs?repo=mozilla-release&revision=f36f7ace6f48&group_state=expanded&filter-tier=3&filter-searchStr=Fxup-release-localtest( [2] - https://treeherder.mozilla.org/#/jobs?repo=mozilla-release&revision=f36f7ace6f48&group_state=expanded&filter-tier=3&filter-searchStr=Fxup-release-cdntest( [3] - https://treeherder.mozilla.org/#/jobs?repo=mozilla-release&revision=f36f7ace6f48&group_state=expanded&filter-tier=3&filter-searchStr=Fxup-release(