Bug 946502. Part 2: Remove unimplemented, unused function. r=mattwoodrow

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extra : rebase_source : fbc4a398d1554ffc668a18bd667b6b90fdace15f
Bug 946502. Part 3: Extend FrameLayerBuilder to set fixed-pos metadata on layers created for background-attachment:fixed content. r=mattwoodrow

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extra : rebase_source : dbaab718d7a358bfaa40124913bcd5acf0255aa1
Bug 946502. Part 4: Remove mStickyPosFrame. r=mattwoodrow

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extra : rebase_source : 71bcbd246cf6806196a3e64d32fdde169bddfa07
Bug 634982. Reftest. r=jrmuizel

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extra : rebase_source : 1ffa269abef40fc16b08c6a34c6bb87906112a82
Bug 941873. Blocked AudioNodeStreams should not run processing. r=karl

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extra : rebase_source : 122b7c48df42f78e9f7d2b8176ff6bc1ca14ad28
Bug 961996 - restore mForceShutDown check before MediaStreamGraphShutDownRunnable dispatch r=roc

This check was dropped in 1ebe4da27dd5.

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extra : rebase_source : 495d81cff39f2ee074effe6bef06caf6b2ac3161