Fix tests to ship Aura overlay scrollbars for ChromeOS

ui/native_theme/native_theme_aura.cc

Index: ui/native_theme/native_theme_aura.cc
diff --git a/ui/native_theme/native_theme_aura.cc b/ui/native_theme/native_theme_aura.cc
index dc7166e6c491181340db32218f2f768dc48c7bab..144bc98a22f32ac5dc15dec0fdda553dfeb8e1bd 100644
--- a/ui/native_theme/native_theme_aura.cc
+++ b/ui/native_theme/native_theme_aura.cc
@@ -174,7 +174,10 @@ void NativeThemeAura::PaintScrollbarTrack(
     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);
@@ -237,7 +240,10 @@ 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);