Adds ability for ash_unittests to run in mushrome mode

mash/test/mash_test_suite.cc

Index: mash/test/mash_test_suite.cc
diff --git a/mash/test/mash_test_suite.cc b/mash/test/mash_test_suite.cc
index 3ca3810207fca7a00dfe3d3976dc1c3d98f5b276..3a6b208c148499ce5647c901c7226201b7f427d3 100644
--- a/mash/test/mash_test_suite.cc
+++ b/mash/test/mash_test_suite.cc
@@ -4,6 +4,8 @@
 
 #include "mash/test/mash_test_suite.h"
 
+#include "ash/public/cpp/config.h"
+#include "ash/test/ash_test_helper.h"
 #include "base/command_line.h"
 #include "base/files/file_path.h"
 #include "base/memory/ptr_util.h"
@@ -41,6 +43,8 @@ void MashTestSuite::Initialize() {
   resources = resources.Append(FILE_PATH_LITERAL("ash_mus_resources.pak"));
   ui::ResourceBundle::InitSharedInstanceWithPakPath(resources);
 
+  ash::test::AshTestHelper::config_ = ash::Config::MASH;
+
   base::DiscardableMemoryAllocator::SetInstance(&discardable_memory_allocator_);
   env_ = aura::Env::CreateInstance(aura::Env::Mode::MUS);