Cros Tablet: Add UMA stats for the user close actions in tablet mode.

ash/frame/caption_buttons/frame_caption_button_container_view.cc

Index: ash/frame/caption_buttons/frame_caption_button_container_view.cc
diff --git a/ash/frame/caption_buttons/frame_caption_button_container_view.cc b/ash/frame/caption_buttons/frame_caption_button_container_view.cc
index 0169b201aa09623d612c9d7116027b2f97636326..7f529cd5bc394d712aca3492dc003745a099f210 100644
--- a/ash/frame/caption_buttons/frame_caption_button_container_view.cc
+++ b/ash/frame/caption_buttons/frame_caption_button_container_view.cc
@@ -338,6 +338,11 @@ void FrameCaptionButtonContainerView::ButtonPressed(views::Button* sender,
   } else if (sender == close_button_) {
     frame_->Close();
     action = UMA_WINDOW_CLOSE_BUTTON_CLICK;
+    if (ash::Shell::Get()
+            ->maximize_mode_controller()
+            ->IsMaximizeModeWindowManagerEnabled()) {
+      action = UMA_TABLET_WINDOW_CLOSE_THROUGH_CAPTION_BUTTON;
+    }
   } else {
     return;
   }