Create DomAgent and CSSAgent in Chrome.

chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h

Index: chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
diff --git a/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h b/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
index 7b9d92ac372da723ad993557dfd7bbdd6ad2f1b9..36947de9477e3944a2f1b594e2aff99dc8627077 100644
--- a/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
+++ b/chrome/browser/ui/views/chrome_browser_main_extra_parts_views.h
@@ -20,6 +20,9 @@ class ViewsDelegate;
 }
 
 #if defined(USE_AURA)
+namespace ui_devtools {
+class UiDevToolsServer;
+}
 namespace views {
 class MusClient;
 }
@@ -45,6 +48,9 @@ class ChromeBrowserMainExtraPartsViews : public ChromeBrowserMainExtraParts {
   std::unique_ptr<views::LayoutProvider> layout_provider_;
 
 #if defined(USE_AURA)
+  // Only used when running in --enable-ui-devtools.
+  std::unique_ptr<ui_devtools::UiDevToolsServer> devtools_server_;
+
   // Not created when running in ash::Config::MUS.
   std::unique_ptr<wm::WMState> wm_state_;