Fix tests to ship Aura overlay scrollbars for ChromeOS

ui/native_theme/native_theme_aura.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/native_theme/native_theme_aura.h"
 
 #include <limits>
 #include <utility>
 
 #include "base/logging.h"
@@ skipping 156 matching lines @@
   PaintArrow(canvas, rect, direction, arrow_color);
 }
 
 void NativeThemeAura::PaintScrollbarTrack(
     SkCanvas* canvas,
     Part part,
     State state,
     const ScrollbarTrackExtraParams& extra_params,
     const gfx::Rect& rect) const {
   // Overlay Scrollbar should never paint a scrollbar track.
-  DCHECK(!IsOverlayScrollbarEnabled());
+  // TODO(bokan/estade): Overlay scrollbars shouldn't be painting a scroll
+  // corner but Views code currently is unaware of Overlays. crbug.com/657159.

[Evan Stade, 2016/11/05 01:13:09]

I don't think this is right. Native scrollbars should go on doing what they're
doing. We have to divorce the overlay-ness of content scrollbars from the
overlay-ness of native scrollbars. It's unfortunate this is not easy to do
because of how the code is structured. You could just remove this DCHECK, but
the other places that use IsOverlayScrollbarEnabled won't be as easy.

I think you'll need to modify NativeTheme::GetInstanceForWeb to return something
that's overlay-aware, and remove references to overlays in NativeThemeAura.

+  if (IsOverlayScrollbarEnabled())
+    return;
   SkPaint paint;
   paint.setColor(kTrackColor);
   canvas->drawIRect(gfx::RectToSkIRect(rect), paint);
 }
 
 void NativeThemeAura::PaintScrollbarThumb(
     SkCanvas* canvas,
     Part part,
     State state,
     const gfx::Rect& rect,
@@ skipping 42 matching lines @@
 
   SkPaint paint;
   paint.setColor(SkColorSetA(thumb_color, thumb_alpha));
   canvas->drawIRect(gfx::RectToSkIRect(thumb_rect), paint);
 }
 
 void NativeThemeAura::PaintScrollbarCorner(SkCanvas* canvas,
                                            State state,
                                            const gfx::Rect& rect) const {
   // Overlay Scrollbar should never paint a scrollbar corner.
-  DCHECK(!IsOverlayScrollbarEnabled());
+  // TODO(bokan/estade): Overlay scrollbars shouldn't be painting a scroll
+  // corner but Views code currently is unaware of Overlays. crbug.com/657159.
+  if (IsOverlayScrollbarEnabled())
+    return;
   SkPaint paint;
   paint.setColor(SkColorSetRGB(0xDC, 0xDC, 0xDC));
   canvas->drawIRect(RectToSkIRect(rect), paint);
 }
 
 gfx::Size NativeThemeAura::GetPartSize(Part part,
                                        State state,
                                        const ExtraParams& extra) const {
   if (IsOverlayScrollbarEnabled()) {
     constexpr int minimum_length =
@@ skipping 13 matching lines @@
         // branch return 0 for parts that don't exist or assert NOTREACHED.
         // crbug.com/657159.
         break;
     }
   }
 
   return NativeThemeBase::GetPartSize(part, state, extra);
 }
 
 }  // namespace ui