Backed out 2 changesets (bug 1358342) for browser-chrome failures on /test/performance/browser_preferences_usage.js on a CLOSED TREE

Backed out changeset f1e4fc4339f7 (bug 1358342)
Backed out changeset 030e811bfc34 (bug 1358342)

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extra : amend_source : 1afeabcf3827be93f84c42965d87d3e5f3806771