Bug 1245164 - Ensure the metrics are still clamped properly when the surface shifts. r=rbarker

--HG--
extra : commitid : 8Y2ITX3hk7i

mobile/android/base/java/org/mozilla/gecko/gfx/NativePanZoomController.java

@@ -190,7 +190,7 @@ class NativePanZoomController extends JNIObject implements PanZoomController {
     @Override // PanZoomController
     public ImmutableViewportMetrics adjustScrollForSurfaceShift(ImmutableViewportMetrics aMetrics, PointF aShift) {
         adjustScrollForSurfaceShift(aShift.x, aShift.y);
-        return aMetrics;
+        return aMetrics.offsetViewportByAndClamp(aShift.x, aShift.y);
     }
 
     @WrapForJNI(allowMultithread = true)