Fix calculation of the bubble view height.

ash/common/system/tray/system_tray.cc

Index: ash/common/system/tray/system_tray.cc
diff --git a/ash/common/system/tray/system_tray.cc b/ash/common/system/tray/system_tray.cc
index 27609771d7d4feceac7ad6445c193a27aa089627..4ca6308eb5a31c5375d616fe76ca4aae1d297ead 100644
--- a/ash/common/system/tray/system_tray.cc
+++ b/ash/common/system/tray/system_tray.cc
@@ -678,7 +678,7 @@ void SystemTray::UpdateWebNotifications() {
             ->GetDisplayNearestWindow(bubble_view->GetWidget()->GetNativeView())
             .work_area();
     height =
-        std::max(0, work_area.height() - bubble_view->GetBoundsInScreen().y());
+        std::max(0, work_area.bottom() - bubble_view->GetBoundsInScreen().y());

[Mr4D (OOO till 08-26), 2017/01/10 15:08:26]

Just wondering - should there be a minumum height instead of 0?

[yhanada, 2017/01/11 01:18:55]

This height doesn't include a height of tray. I think there is no problem that a
minimum height is 0 when no bubble view (e.g. message center or menu) is shown.

   }
   if (web_notification_tray_)
     web_notification_tray_->SetTrayBubbleHeight(height);