Bug 1018255 - Stop fling more quickly when overscrolled. r=kats

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extra : source : 79355b184bc52616567cc16d8f8c61ab31789d67
Bug 1018255 - Don't bother doing the computations in ApplyOverscrollEffect if we are not overscrolled. r=kats

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extra : source : 028af891515ee1093e889d20142f989cb19621b2
Bug 1018255 - Fix a short-circuit evaluation bug in OverscrollSnapBackAnimation::Sample. r=kats

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extra : source : c01a9ce7adb6693dbf5819fe853d4c7076bbd75a
Bug 1018255 - Make the translation (in the direction of overscroll) more pronounced than the zoom. r=kats

--HG--
extra : source : da6418a2a57e4665b2f03e84ff50052902658f45
Bug 1018255 - Use spring physics for snap-back animation. r=kats

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extra : source : f7f4c40fc818c2342fe6c49c0351c1573f6e9f3d