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

ui/views/controls/scroll_view.cc

Index: ui/views/controls/scroll_view.cc
diff --git a/ui/views/controls/scroll_view.cc b/ui/views/controls/scroll_view.cc
index 74cefcc61f7e9dd75aea8fc1593af824d7066290..533f4821edc51aa7e25e2f21d46c29a8a660002e 100644
--- a/ui/views/controls/scroll_view.cc
+++ b/ui/views/controls/scroll_view.cc
@@ -61,13 +61,16 @@ int CheckScrollBounds(int viewport_size, int content_size, int current_pos) {
 }
 
 // Make sure the content is not scrolled out of bounds
-void ConstrainScrollToBounds(View* viewport, View* view) {
+void ConstrainScrollToBounds(View* viewport,
+                             View* view,
+                             bool scroll_with_layers_enabled) {
   if (!view)
     return;
 
   // Note that even when ScrollView::ScrollsWithLayers() is true, the header row
   // scrolls by repainting.
-  const bool scrolls_with_layers = viewport->layer() != nullptr;
+  const bool scrolls_with_layers =
+      scroll_with_layers_enabled && viewport->layer() != nullptr;
   if (scrolls_with_layers) {
     DCHECK(view->layer());
     DCHECK_EQ(0, view->x());
@@ -166,8 +169,11 @@ ScrollView::ScrollView()
   vert_sb_->set_controller(this);
   corner_view_->SetVisible(false);
 
-  if (!base::FeatureList::IsEnabled(kToolkitViewsScrollWithLayers))
+  scroll_with_layers_enabled_ =
+      base::FeatureList::IsEnabled(kToolkitViewsScrollWithLayers);
+  if (!scroll_with_layers_enabled_)
     return;
+
   EnableViewPortLayer();
 }
 
@@ -450,8 +456,10 @@ void ScrollView::Layout() {
   if (header_)
     header_->Layout();
 
-  ConstrainScrollToBounds(header_viewport_, header_);
-  ConstrainScrollToBounds(contents_viewport_, contents_);
+  ConstrainScrollToBounds(header_viewport_, header_,
+                          scroll_with_layers_enabled_);
+  ConstrainScrollToBounds(contents_viewport_, contents_,
+                          scroll_with_layers_enabled_);
   SchedulePaint();
   UpdateScrollBarPositions();
 }
@@ -527,6 +535,16 @@ void ScrollView::OnNativeThemeChanged(const ui::NativeTheme* theme) {
   UpdateBorder();
 }
 
+void ScrollView::ViewHierarchyChanged(
+    const ViewHierarchyChangedDetails& details) {
+  if (details.is_add)

[sky, 2017/04/18 15:35:47]

This should be:
details.is_add && Contains(details.new_parent)

And you should early out if already have a layer.

[ananta, 2017/04/18 22:22:39]

Done.

+    EnableLayeringRecursivelyForChild(details.child);
+}
+
+void ScrollView::OnChildLayerChanged(View* child) {
+  EnableViewPortLayer();
+}
+
 void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
   if (!contents_)
     return;
@@ -717,12 +735,18 @@ void ScrollView::ScrollToOffset(const gfx::ScrollOffset& offset) {
 }
 
 bool ScrollView::ScrollsWithLayers() const {
+  if (!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_));
@@ -763,6 +787,19 @@ void ScrollView::UpdateBorder() {
               : ui::NativeTheme::kColorId_UnfocusedBorderColor)));
 }
 
+bool ScrollView::EnableLayeringRecursivelyForChild(View* view) {
+  if (view->layer()) {

[sky, 2017/04/18 15:35:47]

Early out if viewport_layer_enabled_ or scroll_with_layers_enabled_.

[ananta, 2017/04/18 22:22:39]

Done.

+    EnableViewPortLayer();
+    return true;
+  }
+
+  for (int i = 0; i < view->child_count(); ++i) {
+    if (EnableLayeringRecursivelyForChild(view->child_at(i)))
+      return true;
+  }
+  return false;
+}
+
 // VariableRowHeightScrollHelper ----------------------------------------------
 
 VariableRowHeightScrollHelper::VariableRowHeightScrollHelper(