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

ash/test/ash_test_base.cc

Index: ash/test/ash_test_base.cc
diff --git a/ash/test/ash_test_base.cc b/ash/test/ash_test_base.cc
index 69f5942326fbf8f95df9bdba0d020424058cba8f..c3dde233aae96220911d463116d46a773d7e2588 100644
--- a/ash/test/ash_test_base.cc
+++ b/ash/test/ash_test_base.cc
@@ -89,10 +89,7 @@ class AshEventGeneratorDelegate
 /////////////////////////////////////////////////////////////////////////////
 
 AshTestBase::AshTestBase()
-    : setup_called_(false),
-      teardown_called_(false),
-      start_session_(true),
-      material_mode_(MaterialDesignController::Mode::UNINITIALIZED) {
+    : setup_called_(false), teardown_called_(false), start_session_(true) {
 #if defined(USE_X11)
   // This is needed for tests which use this base class but are run in browser
   // test binaries so don't get the default initialization in the unit test
@@ -130,7 +127,7 @@ void AshTestBase::SetUp() {
                                     "1+1-800x600");
   }
 
-  ash_test_helper_->SetUp(start_session_, material_mode_);
+  ash_test_helper_->SetUp(start_session_);
 
   Shell::GetPrimaryRootWindow()->Show();
   Shell::GetPrimaryRootWindow()->GetHost()->Show();