Prevent notification swipes from getting canceled too soon.

The scroll view was grabbing the gesture as soon as its dy
crossed the scroller's own slop threshold. Once we detect a
horizontal swipe-to-clear we request that the scroller no
longer activate until the gesture is over.

Bug: 4998677
Change-Id: If916fc00d155516e0e4bfe8c2df19827a2f16fe6

packages/SystemUI/src/com/android/systemui/statusbar/policy/NotificationRowLayout.java

@@ -148,6 +148,11 @@ public class NotificationRowLayout extends ViewGroup {
                                 "now sliding child %d: %s (touchY=%.1f, rowHeight=%d, count=%d)",
                                 childIdx, mSlidingChild, mInitialTouchY, mRowHeight, count));
                         }
+
+
+                        // We need to prevent the surrounding ScrollView from intercepting us now;
+                        // the scroll position will be locked while we swipe
+                        requestDisallowInterceptTouchEvent(true);
                     }
                 }
                 break;