Ensure that the focus ring in the bookmarks bar does not paint outside the parent view.

ui/views/controls/scroll_view.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "ui/views/controls/scroll_view.h"
 
 #include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/macros.h"
+#include "base/threading/thread_task_runner_handle.h"
 #include "ui/base/material_design/material_design_controller.h"
 #include "ui/events/event.h"
 #include "ui/gfx/canvas.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
 #include "ui/views/controls/focus_ring.h"
 #include "ui/views/style/platform_style.h"
 #include "ui/views/widget/widget.h"
 
@@ skipping 35 matching lines @@
   int max = std::max(content_size - viewport_size, 0);
   if (current_pos < 0)
     return 0;
   if (current_pos > max)
     return max;
   return current_pos;
 }
 
 // Make sure the content is not scrolled out of bounds
 void ConstrainScrollToBounds(View* viewport, View* view) {
-  if (!view)
+  if (!view || !view->layer())
     return;
 
   // Note that even when ScrollView::ScrollsWithLayers() is true, the header row
   // scrolls by repainting.
   const bool scrolls_with_layers = viewport->layer() != nullptr;
   if (scrolls_with_layers) {
     DCHECK(view->layer());
     DCHECK_EQ(0, view->x());
     DCHECK_EQ(0, view->y());
   }
@@ skipping 19 matching lines @@
                    int content_size,
                    int viewport_size) {
   if (-current_position == new_position)
     return new_position;
   if (new_position < 0)
     return 0;
   const int max_position = std::max(0, content_size - viewport_size);
   return (new_position > max_position) ? max_position : new_position;
 }
 
+// Set if the kToolkitViewsScrollWithLayers feature is enabled.
+// TODO(ananta)
+// Remove this when the feature is enabled by default.
+bool g_scroll_with_layers_enabled = false;
+
 }  // namespace
 
 // Viewport contains the contents View of the ScrollView.
 class ScrollView::Viewport : public View {
  public:
   Viewport() {}
   ~Viewport() override {}
 
   const char* GetClassName() const override { return "ScrollView::Viewport"; }
 
@@ skipping 30 matching lines @@
     : contents_(NULL),
       contents_viewport_(new Viewport()),
       header_(NULL),
       header_viewport_(new Viewport()),
       horiz_sb_(PlatformStyle::CreateScrollBar(true).release()),
       vert_sb_(PlatformStyle::CreateScrollBar(false).release()),
       corner_view_(new ScrollCornerView()),
       min_height_(-1),
       max_height_(-1),
       background_color_(SK_ColorTRANSPARENT),
-      hide_horizontal_scrollbar_(false) {
+      hide_horizontal_scrollbar_(false),
+      weak_ptr_factory_(this) {
   set_notify_enter_exit_on_child(true);
 
   AddChildView(contents_viewport_);
   AddChildView(header_viewport_);
 
   // Don't add the scrollbars as children until we discover we need them
   // (ShowOrHideScrollBar).
   horiz_sb_->SetVisible(false);
   horiz_sb_->set_controller(this);
   vert_sb_->SetVisible(false);
   vert_sb_->set_controller(this);
   corner_view_->SetVisible(false);
 
-  if (!base::FeatureList::IsEnabled(kToolkitViewsScrollWithLayers))
+  g_scroll_with_layers_enabled =
+      base::FeatureList::IsEnabled(kToolkitViewsScrollWithLayers);
+  if (!g_scroll_with_layers_enabled)
     return;
+
   EnableViewPortLayer();
 }
 
 ScrollView::~ScrollView() {
   // The scrollbars may not have been added, delete them to ensure they get
   // deleted.
   delete horiz_sb_;
   delete vert_sb_;
   delete corner_view_;
 }
@@ skipping 339 matching lines @@
 }
 
 const char* ScrollView::GetClassName() const {
   return kViewClassName;
 }
 
 void ScrollView::OnNativeThemeChanged(const ui::NativeTheme* theme) {
   UpdateBorder();
 }
 
+void ScrollView::ChildLayerAdded() {
+  EnableViewPortLayer();
+}
+
 void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
   if (!contents_)
     return;
 
   gfx::ScrollOffset offset = CurrentOffset();
   if (source == horiz_sb_ && horiz_sb_->visible()) {
     position = AdjustPosition(offset.x(), position, contents_->width(),
                               contents_viewport_->width());
     if (offset.x() == position)
       return;
@@ skipping 170 matching lines @@
     // and commits a frame, which isn't true in some tests.
     // See http://crbug.com/637521.
     OnLayerScrolled(offset);
   } else {
     contents_->SetPosition(gfx::Point(-offset.x(), -offset.y()));
     ScrollHeader();
   }
 }
 
 bool ScrollView::ScrollsWithLayers() const {
+  if (!g_scroll_with_layers_enabled)
+    return false;
   // Just check for the presence of a layer since it's cheaper than querying the
   // Feature flag each time.
   return contents_viewport_->layer() != nullptr;
 }
 
 void ScrollView::EnableViewPortLayer() {
+  if (viewport_layer_enabled_)
+    return;
+
+  viewport_layer_enabled_ = true;
   background_color_ = SK_ColorWHITE;
   contents_viewport_->set_background(
       Background::CreateSolidBackground(background_color_));
   contents_viewport_->SetPaintToLayer();
   contents_viewport_->layer()->SetMasksToBounds(true);
 }
 
 void ScrollView::OnLayerScrolled(const gfx::ScrollOffset&) {
   UpdateScrollBarPositions();
   ScrollHeader();
@@ skipping 94 matching lines @@
 
 VariableRowHeightScrollHelper::RowInfo
     FixedRowHeightScrollHelper::GetRowInfo(int y) {
   if (y < top_margin_)
     return RowInfo(0, top_margin_);
   return RowInfo((y - top_margin_) / row_height_ * row_height_ + top_margin_,
                  row_height_);
 }
 
 }  // namespace views