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

ash/wm/toplevel_window_event_handler.cc

Index: ash/wm/toplevel_window_event_handler.cc
diff --git a/ash/wm/toplevel_window_event_handler.cc b/ash/wm/toplevel_window_event_handler.cc
index a0d4b5e7e0b5b589c205c54c0c06f537e04466e9..70ccee35ee47e617152af18b20488eff97f8e726 100644
--- a/ash/wm/toplevel_window_event_handler.cc
+++ b/ash/wm/toplevel_window_event_handler.cc
@@ -10,7 +10,6 @@
 #include "ash/wm/window_properties.h"
 #include "ash/wm/window_resizer.h"
 #include "ash/wm/window_util.h"
-#include "ash/wm/workspace/snap_sizer.h"
 #include "base/message_loop/message_loop.h"
 #include "base/run_loop.h"
 #include "ui/aura/client/aura_constants.h"
@@ -309,9 +308,9 @@ void ToplevelWindowEventHandler::OnGestureEvent(ui::GestureEvent* event) {
             target->layer()->GetAnimator());
         scoped_setter.SetPreemptionStrategy(
             ui::LayerAnimator::REPLACE_QUEUED_ANIMATIONS);
-        internal::SnapSizer::SnapWindow(target,
+        wm::SnapWindowToEdge(target,
             event->details().velocity_x() < 0 ?
-            internal::SnapSizer::LEFT_EDGE : internal::SnapSizer::RIGHT_EDGE);
+            wm::SNAP_LEFT_EDGE : wm::SNAP_RIGHT_EDGE);
       }
       break;
     }