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..18f498cd631a5a86e72ef18112df6f1fa1d8df2e 100644
--- a/ui/views/controls/scroll_view.cc
+++ b/ui/views/controls/scroll_view.cc
@@ -32,6 +32,11 @@ const base::Feature kToolkitViewsScrollWithLayers {
 #endif
 };
 
+// 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;
+
 class ScrollCornerView : public View {
  public:
   ScrollCornerView() {}
@@ -67,7 +72,8 @@ void ConstrainScrollToBounds(View* viewport, View* view) {
 
   // 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 =
+      g_scroll_with_layers_enabled && viewport->layer() != nullptr;

[sky, 2017/04/17 15:24:01]

Make ScrollView have a member for scroll_with_layers_enabled is true and then
pass it into this function. In other words, no global for
g_scroll_with_layers_enabled.

[ananta, 2017/04/18 03:04:25]

Done.

   if (scrolls_with_layers) {
     DCHECK(view->layer());
     DCHECK_EQ(0, view->x());
@@ -166,8 +172,11 @@ 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 +536,10 @@ void ScrollView::OnNativeThemeChanged(const ui::NativeTheme* theme) {
   UpdateBorder();
 }
 
+void ScrollView::OnChildLayerChanged(View* child) {
+  EnableViewPortLayer();
+}
+
 void ScrollView::ScrollToPosition(ScrollBar* source, int position) {
   if (!contents_)
     return;
@@ -717,12 +730,18 @@ 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_));