Fix syncing of system theme on Linux

chrome/browser/themes/theme_service.cc

Index: chrome/browser/themes/theme_service.cc
diff --git a/chrome/browser/themes/theme_service.cc b/chrome/browser/themes/theme_service.cc
index 5d4f0b3fa24a2c5b4ec33392b97333aafb400aff..ed7d1c1525322d3fa9b86632816f1e06cbbd9f98 100644
--- a/chrome/browser/themes/theme_service.cc
+++ b/chrome/browser/themes/theme_service.cc
@@ -119,6 +119,10 @@ gfx::Image ThemeService::GetImageNamed(int id) const {
   return image;
 }
 
+bool ThemeService::IsSystemThemeDistinctFromDefaultTheme() const {
+  return false;
+}
+
 bool ThemeService::UsingSystemTheme() const {
   return UsingDefaultTheme();
 }