Bug 1243359 - initialize mScrollSeriesNumber in all ScrollWheelInput constructors. r=roc

--HG--
extra : transplant_source : %EF%D2%85%C7%97%3E%AA%5E%A6%87%EF5n%89%1D%FDE%F2%B2y

widget/InputData.cpp

@@ -382,6 +382,7 @@ ScrollWheelInput::ScrollWheelInput(const WidgetWheelEvent& aWheelEvent)
   , mDeltaY(aWheelEvent.deltaY)
   , mLineOrPageDeltaX(aWheelEvent.lineOrPageDeltaX)
   , mLineOrPageDeltaY(aWheelEvent.lineOrPageDeltaY)
+  , mScrollSeriesNumber(0)
   , mUserDeltaMultiplierX(1.0)
   , mUserDeltaMultiplierY(1.0)
   , mMayHaveMomentum(aWheelEvent.mayHaveMomentum)