cc/blimp: Add synchronization for scroll/scale state.

blimp/engine/app/settings_manager.cc

Index: blimp/engine/app/settings_manager.cc
diff --git a/blimp/engine/app/settings_manager.cc b/blimp/engine/app/settings_manager.cc
index 50254fdbaff99d7dceb69938ea1fc48303fc8d19..8577b3cbdb8e6125f85f761ff57bf9d5b36a1308 100644
--- a/blimp/engine/app/settings_manager.cc
+++ b/blimp/engine/app/settings_manager.cc
@@ -31,6 +31,7 @@ void SettingsManager::UpdateWebkitPreferences(content::WebPreferences* prefs) {
       settings_.default_maximum_page_scale_factor;
   prefs->shrinks_viewport_contents_to_fit =
       settings_.shrinks_viewport_contents_to_fit;
+  prefs->use_solid_color_scrollbars = true;
 }
 
 const EngineSettings& SettingsManager::GetEngineSettings() const {