Bug 1193062 - Add a PAN_MOMENTUM state. r=kats

This was discussed in bug 1107716.

--HG--
extra : commitid : 8EvQL9qrm3X
extra : rebase_source : 3785c8ac8e7e90f171cf9091f6fc50d76d34f703
extra : histedit_source : ffc8c6cd57f535b03621e149bb300e60683d1612

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -1075,6 +1075,7 @@ nsEventStatus AsyncPanZoomController::OnTouchStart(const MultiTouchInput& aEvent
     case SMOOTH_SCROLL:
     case OVERSCROLL_ANIMATION:
     case WHEEL_SCROLL:
+    case PAN_MOMENTUM:
       CurrentTouchBlock()->GetOverscrollHandoffChain()->CancelAnimations(ExcludeOverscroll);
       // Fall through.
     case NOTHING: {
@@ -1145,6 +1146,7 @@ nsEventStatus AsyncPanZoomController::OnTouchMove(const MultiTouchInput& aEvent)
     case PANNING:
     case PANNING_LOCKED_X:
     case PANNING_LOCKED_Y:
+    case PAN_MOMENTUM:
       TrackTouch(aEvent);
       return nsEventStatus_eConsumeNoDefault;
 
@@ -1209,6 +1211,7 @@ nsEventStatus AsyncPanZoomController::OnTouchEnd(const MultiTouchInput& aEvent)
   case PANNING:
   case PANNING_LOCKED_X:
   case PANNING_LOCKED_Y:
+  case PAN_MOMENTUM:
   {
     CurrentTouchBlock()->GetOverscrollHandoffChain()->FlushRepaints();
     mX.EndTouch(aEvent.mTime);
@@ -1730,6 +1733,7 @@ nsEventStatus AsyncPanZoomController::OnPanMomentumStart(const PanGestureInput&
   }
 
   mPanGestureState = MakeUnique<InputBlockState>(this, true);
+  SetState(PAN_MOMENTUM);
 
   return nsEventStatus_eConsumeNoDefault;
 }
@@ -1744,6 +1748,7 @@ nsEventStatus AsyncPanZoomController::OnPanMomentumEnd(const PanGestureInput& aE
   // animation started, but I guess it doesn't really matter for now.
   mX.CancelTouch();
   mY.CancelTouch();
+  SetState(NOTHING);
 
   RequestContentRepaint();
 

gfx/layers/apz/src/AsyncPanZoomController.h

@@ -754,6 +754,8 @@ protected:
     PANNING_LOCKED_X,         /* touch-start followed by move (i.e. panning with axis lock) X axis */
     PANNING_LOCKED_Y,         /* as above for Y axis */
 
+    PAN_MOMENTUM,             /* like PANNING, but controlled by momentum PanGestureInput events */
+
     CROSS_SLIDING_X,          /* Panning disabled while user does a horizontal gesture
                                  on a vertically-scrollable view. This used for the
                                  Windows Metro "cross-slide" gesture. */