Fix scrollbar buttons on 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 62 matching lines @@
   return NativeThemeAura::instance();
 }
 
 // static
 NativeThemeAura* NativeThemeAura::instance() {
   CR_DEFINE_STATIC_LOCAL(NativeThemeAura, s_native_theme, ());
   return &s_native_theme;
 }
 #endif
 
+bool NativeThemeAura::HasScrollbarButtons() const {
+#if defined(OS_CHROMEOS)
+  // We don't draw scrollbar buttons.
+  return false;
+#else
+  return NativeTheme::HasScrollbarButtons();
+#endif
+}
+
 NativeThemeAura::NativeThemeAura() {
-  // We don't draw scrollbar buttons.
-#if defined(OS_CHROMEOS)
-  set_scrollbar_button_length(0);
-#endif
-
   // Images and alphas declarations assume the following order.
   static_assert(kDisabled == 0, "states unexpectedly changed");
   static_assert(kHovered == 1, "states unexpectedly changed");
   static_assert(kNormal == 2, "states unexpectedly changed");
   static_assert(kPressed == 3, "states unexpectedly changed");
 }
 
 NativeThemeAura::~NativeThemeAura() {
 }
 
@@ skipping 110 matching lines @@
     paint.setColor(SkColorSetA(SK_ColorWHITE, stroke_alpha));
     paint.setStyle(SkPaint::kStroke_Style);
     paint.setStrokeWidth(kStrokeWidth);
     canvas->drawIRect(gfx::RectToSkIRect(thumb_rect), paint);
 
     thumb_rect.Inset(kStrokeWidth, kStrokeWidth, kStrokeWidth, kStrokeWidth);
   } else {
     // If there are no scrollbuttons then provide some padding so that the thumb
     // doesn't touch the top of the track.
     const int kThumbPadding = 2;
-    const int extra_padding =
-        (scrollbar_button_length() == 0) ? kThumbPadding : 0;
+    const int extra_padding = (HasScrollbarButtons()) ? 0 : kThumbPadding;

[esprehn, 2016/05/23 23:11:19]

remove parens

[Bret, 2016/05/23 23:44:06]

Done.

     if (part == NativeTheme::kScrollbarVerticalThumb)
       thumb_rect.Inset(kThumbPadding, extra_padding);
     else
       thumb_rect.Inset(extra_padding, kThumbPadding);
   }
 
   SkPaint paint;
   SkAlpha alpha = gfx::Tween::IntValueBetween(
       progress, ThumbAlphaForState(start_state), ThumbAlphaForState(end_state));
   paint.setColor(SkColorSetA(SK_ColorBLACK, 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());
   SkPaint paint;
   paint.setColor(SkColorSetRGB(0xDC, 0xDC, 0xDC));
   canvas->drawIRect(RectToSkIRect(rect), paint);
 }
 
 }  // namespace ui