Implement Sebastien's overlay scrollbars for native UI (Views).

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 82d852944b656dadf77f632a2663201039b3eb64..2da1f80db5b6d240f2d0b316c1fe773471810161 100644
--- a/ui/views/controls/scrollbar/base_scroll_bar.cc
+++ b/ui/views/controls/scrollbar/base_scroll_bar.cc
@@ -38,7 +38,6 @@ BaseScrollBar::BaseScrollBar(bool horizontal, BaseScrollBarThumb* thumb)
       contents_size_(0),
       contents_scroll_offset_(0),
       viewport_size_(0),
-      thumb_track_state_(CustomButton::STATE_NORMAL),

[Evan Stade, 2016/11/14 16:56:07]

I noticed that this isn't actually used for anything. The thumb track state
doesn't affect appearance for this or any other scrollbar. The repeater is
affected by calling SetState, so that functionality had to be salvaged.

       last_scroll_amount_(SCROLL_NONE),
       repeater_(base::Bind(&BaseScrollBar::TrackClicked,
                            base::Unretained(this))),
@@ -112,15 +111,6 @@ bool BaseScrollBar::ScrollByContentsOffset(int contents_offset) {
   return true;
 }
 
-void BaseScrollBar::OnThumbStateChanged(CustomButton::ButtonState old_state,
-                                        CustomButton::ButtonState new_state) {
-  if (old_state == CustomButton::STATE_PRESSED &&
-      new_state == CustomButton::STATE_NORMAL &&
-      GetThumbTrackState() == CustomButton::STATE_HOVERED) {
-    SetThumbTrackState(CustomButton::STATE_NORMAL);
-  }
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // BaseScrollBar, View implementation:
 
@@ -131,21 +121,11 @@ bool BaseScrollBar::OnMousePressed(const ui::MouseEvent& event) {
 }
 
 void BaseScrollBar::OnMouseReleased(const ui::MouseEvent& event) {
-  SetState(HitTestPoint(event.location()) ?
-           CustomButton::STATE_HOVERED : CustomButton::STATE_NORMAL);
+  repeater_.Stop();
 }
 
 void BaseScrollBar::OnMouseCaptureLost() {
-  SetState(CustomButton::STATE_NORMAL);
-}
-
-void BaseScrollBar::OnMouseEntered(const ui::MouseEvent& event) {
-  SetThumbTrackState(CustomButton::STATE_HOVERED);
-}
-
-void BaseScrollBar::OnMouseExited(const ui::MouseEvent& event) {
-  if (GetThumbTrackState() == CustomButton::STATE_HOVERED)
-    SetState(CustomButton::STATE_NORMAL);
+  repeater_.Stop();
 }
 
 bool BaseScrollBar::OnKeyPressed(const ui::KeyEvent& event) {
@@ -216,7 +196,7 @@ void BaseScrollBar::OnGestureEvent(ui::GestureEvent* event) {
     return;
   }
 
-  SetState(CustomButton::STATE_NORMAL);
+  repeater_.Stop();
 
   if (event->type() == ui::ET_GESTURE_TAP) {
     // TAP_DOWN would have already scrolled some amount. So scrolling again on
@@ -407,8 +387,7 @@ void BaseScrollBar::Update(int viewport_size,
   // content size multiplied by the height of the thumb track.
   double ratio =
       std::min(1.0, static_cast<double>(viewport_size) / contents_size_);
-  int thumb_size = static_cast<int>(ratio * GetTrackSize());
-  thumb_->SetSize(thumb_size);
+  thumb_->SetLength(static_cast<int>(ratio * GetTrackSize()));
 
   int thumb_position = CalculateThumbPosition(contents_scroll_offset);
   thumb_->SetPosition(thumb_position);
@@ -425,10 +404,6 @@ BaseScrollBarThumb* BaseScrollBar::GetThumb() const {
   return thumb_;
 }
 
-CustomButton::ButtonState BaseScrollBar::GetThumbTrackState() const {
-  return thumb_track_state_;
-}
-
 void BaseScrollBar::ScrollToPosition(int position) {
   controller()->ScrollToPosition(this, position);
 }
@@ -445,7 +420,6 @@ int BaseScrollBar::GetThumbSizeForTest() {
 }
 
 void BaseScrollBar::ProcessPressEvent(const ui::LocatedEvent& event) {
-  SetThumbTrackState(CustomButton::STATE_PRESSED);
   gfx::Rect thumb_bounds = thumb_->bounds();
   if (IsHorizontal()) {
     if (GetMirroredXInView(event.x()) < thumb_bounds.x()) {
@@ -464,11 +438,6 @@ void BaseScrollBar::ProcessPressEvent(const ui::LocatedEvent& event) {
   repeater_.Start();
 }
 
-void BaseScrollBar::SetState(CustomButton::ButtonState state) {
-  SetThumbTrackState(state);
-  repeater_.Stop();
-}
-
 void BaseScrollBar::TrackClicked() {
   if (last_scroll_amount_ != SCROLL_NONE)
     ScrollByAmount(last_scroll_amount_);
@@ -507,9 +476,4 @@ int BaseScrollBar::CalculateContentsOffset(int thumb_position,
          (track_size - thumb_size);
 }
 
-void BaseScrollBar::SetThumbTrackState(CustomButton::ButtonState state) {
-  thumb_track_state_ = state;
-  SchedulePaint();

[Evan Stade, 2016/11/14 16:56:07]

there was a lot of extra painting for no reason... :/

-}
-
 }  // namespace views