Bug 892274 - H should toggle the selected node's hidden attribute. r=harth

--HG--
extra : rebase_source : 2e56afd40e611dc2d6d87d1c7c978e64ebb90baf
Bug 892277 - Change stepping hotkeys. r=fitzgen

--HG--
extra : rebase_source : 485d6a4d7f16186c2fc452e3c6bb652d1842e40c