fix typos in GestureDetector syncConstructorArguments

packages/flutter/lib/src/widgets/gesture_detector.dart

@@ -52,12 +52,12 @@ class GestureDetector extends StatefulComponent {
     onTap = source.onTap;
     onShowPress = source.onShowPress;
     onLongPress = source.onLongPress;
-    onVerticalScrollStart = onVerticalScrollStart;
-    onVerticalScrollUpdate = onVerticalScrollUpdate;
-    onVerticalScrollEnd = onVerticalScrollEnd;
-    onHorizontalScrollStart = onHorizontalScrollStart;
-    onHorizontalScrollUpdate = onHorizontalScrollUpdate;
-    onHorizontalScrollEnd = onHorizontalScrollEnd;
+    onVerticalScrollStart = source.onVerticalScrollStart;
+    onVerticalScrollUpdate = source.onVerticalScrollUpdate;
+    onVerticalScrollEnd = source.onVerticalScrollEnd;
+    onHorizontalScrollStart = source.onHorizontalScrollStart;
+    onHorizontalScrollUpdate = source.onHorizontalScrollUpdate;
+    onHorizontalScrollEnd = source.onHorizontalScrollEnd;
     onPanStart = source.onPanStart;
     onPanUpdate = source.onPanUpdate;
     onPanEnd = source.onPanEnd;

packages/flutter/lib/src/widgets/scrollable.dart

@@ -558,10 +558,6 @@ class PageableList<T> extends ScrollableList<T> {
       .clamp(scrollBehavior.minScrollOffset, scrollBehavior.maxScrollOffset);
   }
 
-  EventDisposition _handlePointerDown(_) {
-    return EventDisposition.ignored;
-  }
-
   EventDisposition _handleFlingStart(sky.GestureEvent event) {
     double velocity = _eventVelocity(event);
     double newScrollOffset = _snapScrollOffset(scrollOffset + velocity.sign * itemExtent)