Bug 1105109 - Introduce a FrameMetrics::ClampAndSetScrollOffset() helper. r=kats

MozReview-Commit-ID: 6LCPKrdGM6M

--HG--
extra : rebase_source : 65f51ce5c40d9f1ac64c1f94055aa87d44a72cae

gfx/layers/FrameMetrics.h

@@ -335,6 +335,12 @@ public:
     mScrollOffset = aScrollOffset;
   }
 
+  // Set scroll offset, first clamping to the scroll range.
+  void ClampAndSetScrollOffset(const CSSPoint& aScrollOffset)
+  {
+    SetScrollOffset(CalculateScrollRange().ClampPoint(aScrollOffset));
+  }
+
   const CSSPoint& GetScrollOffset() const
   {
     return mScrollOffset;

gfx/layers/apz/src/AsyncPanZoomController.cpp

@@ -582,10 +582,9 @@ public:
       // offset to end up being a bit off from the destination, we can get
       // artefacts like "scroll to the next snap point in this direction"
       // scrolling to the snap point we're already supposed to be at.
-      aFrameMetrics.SetScrollOffset(
-          aFrameMetrics.CalculateScrollRange().ClampPoint(
-              CSSPoint::FromAppUnits(nsPoint(mXAxisModel.GetDestination(),
-                                             mYAxisModel.GetDestination()))));
+      aFrameMetrics.ClampAndSetScrollOffset(
+          CSSPoint::FromAppUnits(nsPoint(mXAxisModel.GetDestination(),
+                                         mYAxisModel.GetDestination())));
       return false;
     }
 
@@ -3789,9 +3788,7 @@ void AsyncPanZoomController::NotifyLayersUpdated(const ScrollMetadata& aScrollMe
       // Even if we didn't accept a new scroll offset from content, the
       // scrollable rect may have changed in a way that makes our local
       // scroll offset out of bounds, so re-clamp it.
-      mFrameMetrics.SetScrollOffset(
-          mFrameMetrics.CalculateScrollRange().ClampPoint(
-              mFrameMetrics.GetScrollOffset()));
+      mFrameMetrics.ClampAndSetScrollOffset(mFrameMetrics.GetScrollOffset());
     }
   }