Fix the white background regression on the Extensions overflow menu.

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 "ui/base/material_design/material_design_controller.h"
@@ skipping 729 matching lines @@
   // 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();

[sky, 2017/05/22 16:23:40]

Does supplying LAYER_SOLID_COLOR work for your needs? That's preferable as a
solid color layer takes up less gpu memory.

[ananta, 2017/05/22 19:22:43]

Sadly no. The content does not show up.

+
+  if (scroll_with_layers_enabled_) {
+    background_color_ = SK_ColorWHITE;
+    contents_viewport_->set_background(
+        Background::CreateSolidBackground(background_color_));
+  } else {
+    // We may have transparent children who want to blend into the default
+    // background.
+    contents_viewport_->layer()->SetFillsBoundsOpaquely(false);
+  }
   contents_viewport_->layer()->SetMasksToBounds(true);
 }
 
 void ScrollView::OnLayerScrolled(const gfx::ScrollOffset&) {
   UpdateScrollBarPositions();
   ScrollHeader();
 }
 
 void ScrollView::ScrollHeader() {
   if (!header_)
@@ skipping 106 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