overview: Remove unused includes in overview_controller.cc

They were for OverviewController::OnOverviewButtonTrayLongPressed which
was moved to SplitViewController in
https://chromium-review.googlesource.com/c/chromium/src/+/2024447

Bug: None
Change-Id: Id1e0b88c50f05d292040a7a9f04d83bd762c2d1b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2040382Reviewed-by: Sammie Quon <sammiequon@chromium.org>
Commit-Queue: Avery Musbach <amusbach@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738761}

ash/wm/overview/overview_controller.cc

@@ -22,18 +22,15 @@
 #include "ash/wm/overview/overview_wallpaper_controller.h"
 #include "ash/wm/screen_pinning_controller.h"
 #include "ash/wm/splitview/split_view_controller.h"
-#include "ash/wm/splitview/split_view_utils.h"
 #include "ash/wm/tablet_mode/tablet_mode_controller.h"
 #include "ash/wm/window_state.h"
 #include "ash/wm/window_util.h"
 #include "base/bind.h"
 #include "base/containers/unique_ptr_adapters.h"
 #include "base/metrics/histogram_macros.h"
-#include "base/metrics/user_metrics.h"
 #include "base/stl_util.h"
 #include "base/threading/thread_task_runner_handle.h"
 #include "ui/views/widget/widget.h"
-#include "ui/wm/core/window_util.h"
 #include "ui/wm/public/activation_client.h"
 
 namespace ash {