Fixes velocity tracking bug in SwipeDismissLayout.

This is the framework version of ag/682710.
Original change description:
This change adds a missing call to offsetLocation() when tracking
swipe velocities on a SwipeDismissLayout.  This bug was causing
incorrect velocities to be measured which often resulted in an
incorrectly interpreted leftward swipe cancelling the dismiss
gesture.

Bug: 20350515
Change-Id: I4f3e3668a1f9aab963fdfa9095a43f4c5344703f

core/java/com/android/internal/widget/SwipeDismissLayout.java

@@ -216,6 +216,8 @@ public class SwipeDismissLayout extends FrameLayout {
         if (mVelocityTracker == null) {
             return super.onTouchEvent(ev);
         }
+        // offset because the view is translated during swipe
+        ev.offsetLocation(mTranslationX, 0);
         switch (ev.getActionMasked()) {
             case MotionEvent.ACTION_UP:
                 updateDismiss(ev);