ash: Reset |presentation_time_recorder| when drag is completed.

|presentation_time_recorder| will be released with the
WorkspaceWindowResizer after the drag ends. However, in TAST testing,
metrics is collected before WorkspaceWindowResizer gets released. If we
don't release the recorder when drag is completed, the metrics will not
be collected correctly and timeout errors may occur.

Bug: 1032766
Change-Id: I7c7788ffc1255a33c47b41833813226de24f6531
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2211882
Commit-Queue: Yichen Zhou <yichenz@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#771193}

ash/wm/workspace/workspace_window_resizer.cc

@@ -586,6 +586,8 @@ void WorkspaceWindowResizer::Drag(const gfx::PointF& location_in_parent,
 }
 
 void WorkspaceWindowResizer::CompleteDrag() {
+  tab_dragging_recorder_.reset();
+
   gfx::PointF last_mouse_location_in_screen = last_mouse_location_;
   ::wm::ConvertPointToScreen(GetTarget()->parent(),
                              &last_mouse_location_in_screen);
@@ -687,6 +689,8 @@ void WorkspaceWindowResizer::CompleteDrag() {
 }
 
 void WorkspaceWindowResizer::RevertDrag() {
+  tab_dragging_recorder_.reset();
+
   gfx::PointF last_mouse_location_in_screen = last_mouse_location_;
   ::wm::ConvertPointToScreen(GetTarget()->parent(),
                              &last_mouse_location_in_screen);