Gtk3: Fallback on using Aura alert icon colors

chrome/browser/ui/libgtkui/native_theme_gtk3.cc

 // 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.
 
 #include "chrome/browser/ui/libgtkui/native_theme_gtk3.h"
 
 #include <gtk/gtk.h>
 
 #include "chrome/browser/ui/libgtkui/chrome_gtk_frame.h"
 #include "chrome/browser/ui/libgtkui/chrome_gtk_menu_subclasses.h"
@@ skipping 336 matching lines @@
 
     // Throbber
     // TODO(thomasanderson): Render GtkSpinner directly.
     case ui::NativeTheme::kColorId_ThrobberSpinningColor:
     case ui::NativeTheme::kColorId_ThrobberWaitingColor:
       return GetFgColor("GtkMenu#menu GtkSpinner#spinner");
     case ui::NativeTheme::kColorId_ThrobberLightColor:
       return GetFgColor("GtkMenu#menu GtkSpinner#spinner:disabled");
 
     // Alert icons
+    // Fallback to the same colors as Aura.
     case ui::NativeTheme::kColorId_AlertSeverityLow:
-      return GetBgColor("GtkInfoBar#infobar.info");
     case ui::NativeTheme::kColorId_AlertSeverityMedium:
-      return GetBgColor("GtkInfoBar#infobar.warning");
-    case ui::NativeTheme::kColorId_AlertSeverityHigh:
-      return GetBgColor("GtkInfoBar#infobar.error");
+    case ui::NativeTheme::kColorId_AlertSeverityHigh: {
+      // Alert icons appear on the toolbar, so use the toolbar BG
+      // color to determine if the dark Aura theme should be used.
+      ui::NativeTheme* fallback_theme =
+          color_utils::IsDark(GetBgColor("GtkToolbar#toolbar"))
+              ? ui::NativeTheme::GetInstanceForNativeUi()
+              : ui::NativeThemeDarkAura::instance();
+      return fallback_theme->GetSystemColor(color_id);
+    }
 
     case ui::NativeTheme::kColorId_NumColors:
       NOTREACHED();
       break;
   }
   return kInvalidColorIdColor;
 }
 
 void OnThemeChanged(GObject* obj, GParamSpec* param, NativeThemeGtk3* theme) {
   theme->ResetColorCache();
@@ skipping 214 matching lines @@
 
   if (frame_top_area.incognito) {
     bitmap = SkBitmapOperations::CreateHSLShiftedBitmap(
         bitmap, kDefaultTintFrameIncognito);
   }
 
   canvas->drawBitmap(bitmap, rect.x(), rect.y());
 }
 
 }  // namespace libgtkui