Only support left/right maximizing at 50% width when the --ash-enable-alternate-caption-button

ash/wm/gestures/two_finger_drag_handler.cc

Index: ash/wm/gestures/two_finger_drag_handler.cc
diff --git a/ash/wm/gestures/two_finger_drag_handler.cc b/ash/wm/gestures/two_finger_drag_handler.cc
index 49f7ecc02dd530562bc4ea759a95a19b28e0197a..bde37ed9969534ff71aa6bef6427db437bc6c22e 100644
--- a/ash/wm/gestures/two_finger_drag_handler.cc
+++ b/ash/wm/gestures/two_finger_drag_handler.cc
@@ -142,14 +142,17 @@ bool TwoFingerDragHandler::ProcessGestureEvent(aura::Window* target,
       } else if (event.details().swipe_down() &&
                  wm::CanMinimizeWindow(target)) {
         wm::MinimizeWindow(target);
-      } else if (wm::CanSnapWindow(target)) {
-        ui::ScopedLayerAnimationSettings scoped_setter(
-            target->layer()->GetAnimator());
-        scoped_setter.SetPreemptionStrategy(
-            ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
-        internal::SnapSizer::SnapWindow(target,
-            event.details().swipe_left() ? internal::SnapSizer::LEFT_EDGE :
-                                           internal::SnapSizer::RIGHT_EDGE);
+      } else {
+        using internal::SnapSizer;
+        SnapSizer::Edge edge = event.details().swipe_left() ?
+            SnapSizer::LEFT_EDGE : SnapSizer::RIGHT_EDGE;
+        if (SnapSizer::CanSnapWindow(target, edge)) {
+          ui::ScopedLayerAnimationSettings scoped_setter(
+              target->layer()->GetAnimator());
+          scoped_setter.SetPreemptionStrategy(
+              ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
+          SnapSizer::SnapWindow(target, edge, SnapSizer::STEP_NO);
+        }
       }
       return true;
     }