Gut ash::MaterialDesignController, and remove the about:flags entry.

ash/shell/content/client/shell_browser_main_parts.cc

Index: ash/shell/content/client/shell_browser_main_parts.cc
diff --git a/ash/shell/content/client/shell_browser_main_parts.cc b/ash/shell/content/client/shell_browser_main_parts.cc
index 02592967f5e8b2219b6a58b3df5a7b3e7c957eb5..84299c3ce1830400ceb28219502e3985b9fc11b6 100644
--- a/ash/shell/content/client/shell_browser_main_parts.cc
+++ b/ash/shell/content/client/shell_browser_main_parts.cc
@@ -5,7 +5,6 @@
 #include "ash/shell/content/client/shell_browser_main_parts.h"
 
 #include "ash/common/login_status.h"
-#include "ash/common/material_design/material_design_controller.h"
 #include "ash/common/wm_shell.h"
 #include "ash/content/shell_content_state.h"
 #include "ash/shell.h"
@@ -100,7 +99,6 @@ void ShellBrowserMainParts::PostMainMessageLoopStart() {
 }
 
 void ShellBrowserMainParts::ToolkitInitialized() {
-  ash::MaterialDesignController::Initialize();
   wm_state_.reset(new ::wm::WMState);
 }