Backed out 4 changesets (bug 887690) for suspicion of causing frequent mochitest-2 failures.

Backed out changeset 106ae6eee902 (bug 887690)
Backed out changeset e2c72cb029f4 (bug 887690)
Backed out changeset 9eea090ed6f7 (bug 887690)
Backed out changeset 1defeb691f5c (bug 887690)