Bug 883314 part 1: simplify code, r=jmaher

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Bug 883314 part 2: refactor mochitest chunking code to be re-used for mochitest-browser-chrome, r=jmaher

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extra : transplant_source : %0A%C3%7F%B7%CFL%AD%2C%A2Y%5D51%AF%19%C1%C8%C5%5B%07
Bug 883314 part 3: adjust refactored chunking code to deal with mochitest-browser-chrome and mochitest-chrome file paths, r=jmaher

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extra : transplant_source : %ED%E7%ED%EEs%C5.%A0%FE%3ECEI60%A4h%C2%11Y
Bug 883314 part 4: use the chunking code for mochitest-browser-chrome, r=jmaher

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extra : transplant_source : E%26%86p%E0%14%99Jb%19%A8%A8%D9%23%7E%9EiH%DBf
Bug 883634: merge harness-overlay.xul into overlay.xul, r=jmaher

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extra : transplant_source : SO%03%F2n%FD%91%1C%1E%05%0C%BE%284%EE%1E%93%91%E5%7B
Bug 880101: fix intermittent orange in browser_locationBarCommand.js, r=margaret

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extra : transplant_source : Y%B2%A3%D5i%2C%8F%CB%FA%82%B1%83%A2%BB%96%99q%C8%B7%FA
Bug 879658: avoiding exposing localStorage to non-whitelisted social providers, r=mixedpuppy

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extra : transplant_source : %15%905%E6%D9%A2%B5%85%D9%1C%01%A1%9F%18%9C%9F%28%93%7D%1A
Bug 860560: make sure that defaultEngine and currentEngine stay in sync, r=gavin

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extra : transplant_source : %83%A6%F6%02%C5a6%08%09/%3C%D4p%23%0BI%EF%EE%C0%16
Bug 493051: avoid having addEngine select the engine by default, by adding an optional callback to let callers observe the successful addition of the engine, r=MattN

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extra : transplant_source : M%40%CB%E5%8F%D9RMc%BA%23%20%C7%EC%9A%84H%DB%1B%81
Bug 867108: hiding and then restoring the default search engine leads to the wrong engine being returned from searchService.defaultEngine until a restart, r=mikedeboer

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rename : toolkit/components/search/tests/xpcshell/test_engineselect.js => toolkit/components/search/tests/xpcshell/test_defaultEngine.js
extra : transplant_source : %2C%EE2%EF%EA%8Ak%D8%18%21%BB%98%18%14%BE%E9t%82%7C%BF