Gtk3: Fix black patches on GtkFileChooser dialogs

chrome/browser/ui/libgtkui/native_theme_gtk3.h

 // Copyright 2016 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.
 
 #ifndef CHROME_BROWSER_UI_LIBGTKUI_NATIVE_THEME_GTK3_H_
 #define CHROME_BROWSER_UI_LIBGTKUI_NATIVE_THEME_GTK3_H_
 
 #include "base/macros.h"
 #include "base/optional.h"
+#include "ui/base/glib/glib_signal.h"
+#include "ui/base/glib/scoped_gobject.h"
 #include "ui/native_theme/native_theme_base.h"
 
+typedef struct _GtkCssProvider GtkCssProvider;
+typedef struct _GtkParamSpec GtkParamSpec;
+typedef struct _GtkSettings GtkSettings;
+
 namespace libgtkui {
 
+using ScopedCssProvider = ScopedGObject<GtkCssProvider>;
+
 // A version of NativeTheme that uses GTK3-rendered widgets.
 class NativeThemeGtk3 : public ui::NativeThemeBase {
  public:
   static NativeThemeGtk3* instance();
 
-  // Called when gtk theme changes.
-  void ResetColorCache();
-
   // Overridden from ui::NativeThemeBase:
   SkColor GetSystemColor(ColorId color_id) const override;
   void PaintArrowButton(cc::PaintCanvas* canvas,
                         const gfx::Rect& rect,
                         Part direction,
                         State state) const override;
   void PaintScrollbarTrack(cc::PaintCanvas* canvas,
                            Part part,
                            State state,
                            const ScrollbarTrackExtraParams& extra_params,
@@ skipping 24 matching lines @@
   void PaintFrameTopArea(
       cc::PaintCanvas* canvas,
       State state,
       const gfx::Rect& rect,
       const FrameTopAreaExtraParams& frame_top_area) const override;
 
  private:
   NativeThemeGtk3();
   ~NativeThemeGtk3() override;
 
+  void SetThemeCssOverride(ScopedCssProvider provider);
+
+  CHROMEG_CALLBACK_1(NativeThemeGtk3,
+                     void,
+                     OnThemeChanged,
+                     GtkSettings*,
+                     GtkParamSpec*);
+
   mutable base::Optional<SkColor> color_cache_[kColorId_NumColors];
 
+  ScopedCssProvider theme_css_override_;
+
   DISALLOW_COPY_AND_ASSIGN(NativeThemeGtk3);
 };
 
 }  // namespace libgtkui
 
 #endif  // CHROME_BROWSER_UI_LIBGTKUI_NATIVE_THEME_GTK3_H_