Bug 1017110 - Suppress warnings in third-party code: libstagefright. r=cajbir

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extra : rebase_source : 7bb135a1ac1cdeda748fcfb6a2a6283807259e80
Bug 1018270 - Part 1: Cherrypick -Wunused-private-field warning fix from upstream gtest. r=ted

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extra : rebase_source : 45cdafffe4416cfbaa14a3a30305c4d2ce570992
Bug 1018554 - Fix WebMWriter warnings and mark content/media/gtest as FAIL_ON_WARNINGS. r=rillian

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extra : rebase_source : 43a93774466cc6d7f3e1f409d63c1663b1870149