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..fc3c76e9fb2e002d1bddfedecf3f9857196d5c0b 100644
--- a/ui/views/controls/scroll_view.cc
+++ b/ui/views/controls/scroll_view.cc
@@ -7,6 +7,7 @@
 #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"
@@ -62,7 +63,7 @@ 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) {
-  if (!view)
+  if (!view || !view->layer())
     return;
 
   // Note that even when ScrollView::ScrollsWithLayers() is true, the header row
@@ -102,6 +103,11 @@ int AdjustPosition(int current_position,
   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.
@@ -152,7 +158,8 @@ ScrollView::ScrollView()
       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_);
@@ -166,8 +173,11 @@ ScrollView::ScrollView()
   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();
 }
 
@@ -527,6 +537,10 @@ void ScrollView::OnNativeThemeChanged(const ui::NativeTheme* theme) {
   UpdateBorder();
 }
 
+void ScrollView::ChildLayerAdded() {
+  EnableViewPortLayer();
+}
+
 void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
   if (!contents_)
     return;
@@ -717,12 +731,18 @@ void ScrollView::ScrollToOffset(const gfx::ScrollOffset& offset) {
 }
 
 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_));