MacViews: Overlay Scrollbars with Show/Hide Animations

ui/views/controls/scrollbar/base_scroll_bar.cc

Index: ui/views/controls/scrollbar/base_scroll_bar.cc
diff --git a/ui/views/controls/scrollbar/base_scroll_bar.cc b/ui/views/controls/scrollbar/base_scroll_bar.cc
index 117fe345dffea247bef217e0c73e1210d7ea7b24..97194a9066e42ceb954c6d4dcbac27b4da0d6674 100644
--- a/ui/views/controls/scrollbar/base_scroll_bar.cc
+++ b/ui/views/controls/scrollbar/base_scroll_bar.cc
@@ -128,6 +128,20 @@ void BaseScrollBar::OnThumbStateChanged(CustomButton::ButtonState old_state,
 ///////////////////////////////////////////////////////////////////////////////
 // BaseScrollBar, View implementation:
 
+void BaseScrollBar::Layout() {

[tapted, 2016/02/22 04:42:15]

If we keep this here, the identical logic can be removed from
overlay_scroll_bar.cc

However, I just tried it out, and I think this can be simplified to just
`GetThumb()->SetBoundsRect(GetTrackBounds())` (in CocoaScrollBar)

That's what NativeScrollBarViews does, but since it's just one line, I think
it's fine to just put it in CocoaScrollBar, and remove the default-provided
implementation (make BaseScrollBar::Layout() pure virtual again). (I think this
will be more appealing to OWNERS too, but beforehand it was too much duplicated
logic).

[spqchan, 2016/02/22 19:01:37]

Done.

+  // Provide a default implementation that sets the thumb's bounds in the
+  // scrollbar.
+  gfx::Rect thumb_bounds = GetTrackBounds();
+  if (IsHorizontal()) {
+    thumb_bounds.set_x(thumb_->x());
+    thumb_bounds.set_width(thumb_->width());
+  } else {
+    thumb_bounds.set_y(thumb_->y());
+    thumb_bounds.set_height(thumb_->height());
+  }
+  thumb_->SetBoundsRect(thumb_bounds);
+}
+
 bool BaseScrollBar::OnMousePressed(const ui::MouseEvent& event) {
   if (event.IsOnlyLeftMouseButton())
     ProcessPressEvent(event);