Bug 1042974 - Dispatch flings to the right scrollable element in the presence of scrollgrab. r=kats

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extra : rebase_source : b2282c8fb958d91160d7b89790baf97ada591804
Bug 1042974 - Gtests for scrollgrab. r=kats

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extra : rebase_source : 1de35060a59c594bde0c7c003775b32fb71b6d51
Bug 1025436 - Return true from AsyncPanZoomController::AdvanceAnimations() if one of the deferred tasks started a new animation. r=kats

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extra : rebase_source : 82978c55141b9a3ef05dff2273edd5c84dace479
Bug 1025436 - Gtest for flinging into overscroll. r=kats

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extra : rebase_source : 04f121408c43826ac67e71acb229cfcaad137c3e