mus: Use a cmd flag when mus is hosting viz.

Use --mus=viz if the mus window-server is the viz-host. If --mus is
not set to viz, then mus is used, but chrome still is the viz host.

For now, always set it to 'viz', so that mus still remains the viz
host. Once some more fixes land, we can turn it off by default.

BUG=786453

Change-Id: If8f6fca0178322311a0a14b718b08f9084bda35c
Reviewed-on: https://chromium-review.googlesource.com/792276
Commit-Queue: Sadrul Chowdhury <sadrul@chromium.org>
Reviewed-by: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519840}

ash/test/ash_test_suite.cc

@@ -17,6 +17,7 @@
 #include "ui/aura/test/aura_test_context_factory.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/base/ui_base_paths.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/gfx/gfx_paths.h"
 #include "ui/gl/test/gl_surface_test_support.h"
 
@@ -73,6 +74,9 @@ void AshTestSuite::Initialize() {
     context_factory_ = std::make_unique<aura::test::AuraTestContextFactory>();
     env_->set_context_factory(context_factory_.get());
     env_->set_context_factory_private(nullptr);
+    // mus needs to host viz, because ash by itself cannot.
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
   }
 }
 

chrome/app/chrome_main.cc

@@ -105,11 +105,6 @@ int ChromeMain(int argc, const char** argv) {
 #endif  // defined(OS_LINUX) || defined(OS_MACOSX) || defined(OS_WIN)
 
 #if BUILDFLAG(ENABLE_MUS)
-  if (service_manager::ServiceManagerIsRemote() ||
-      command_line->HasSwitch(switches::kMash)) {
-    params.create_discardable_memory = false;
-    params.env_mode = aura::Env::Mode::MUS;
-  }
   // In config==mus the ui service runs in process and is shut down well before
   // the rest of Chrome. Have Chrome create the DiscardableSharedMemoryManager
   // to ensure the DiscardableSharedMemoryManager is destroyed later on. Doing
@@ -119,6 +114,16 @@ int ChromeMain(int argc, const char** argv) {
   if (command_line->HasSwitch(switches::kMus)) {
     params.create_discardable_memory = true;
     params.env_mode = aura::Env::Mode::MUS;
+    // TODO(786453): Remove when mus no longer needs to host viz.
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
+  }
+  if (service_manager::ServiceManagerIsRemote() ||
+      command_line->HasSwitch(switches::kMash)) {
+    params.create_discardable_memory = false;
+    params.env_mode = aura::Env::Mode::MUS;
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
   }
 #endif  // BUILDFLAG(ENABLE_MUS)
 

chrome/browser/chromeos/first_run/goodies_displayer_browsertest.cc

@@ -85,10 +85,9 @@ class GoodiesDisplayerBrowserTest : public InProcessBrowserTest,
   // InProcessBrowserTest overrides.
   void SetUpDefaultCommandLine(base::CommandLine* command_line) override {
     base::CommandLine default_command_line(base::CommandLine::NO_PROGRAM);
-    if (command_line->HasSwitch(switches::kMash))
-      default_command_line.AppendSwitch(switches::kMash);
-    else if (command_line->HasSwitch(switches::kMus))
-      default_command_line.AppendSwitch(switches::kMus);
+    const char* kSwitchesToCopy[] = {switches::kMash, switches::kMus};
+    default_command_line.CopySwitchesFrom(*command_line, kSwitchesToCopy,
+                                          arraysize(kSwitchesToCopy));
     InProcessBrowserTest::SetUpDefaultCommandLine(&default_command_line);
     if (NoFirstRunSpecified()) {  // --no-first-run is present by default.
       *command_line = default_command_line;

chrome/test/base/mash_browser_tests_main.cc

@@ -42,6 +42,8 @@ class MusTestLauncherDelegate : public ChromeTestLauncherDelegate {
     content::GetContentMainParams()->env_mode = aura::Env::Mode::MUS;
     content::GetContentMainParams()->create_discardable_memory =
         (config_ == AshConfig::MUS);
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
     return ChromeTestLauncherDelegate::RunTestSuite(argc, argv);
   }
 

content/browser/browser_main_loop.cc

@@ -130,6 +130,7 @@
 #include "third_party/boringssl/src/include/openssl/evp.h"
 #include "ui/base/clipboard/clipboard.h"
 #include "ui/base/ui_base_switches.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/display/display_switches.h"
 #include "ui/gfx/switches.h"
 
@@ -1454,9 +1455,6 @@ int BrowserMainLoop::BrowserThreadsStarted() {
 
 #if BUILDFLAG(ENABLE_MUS)
   if (IsUsingMus()) {
-    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
-        switches::kMus,
-        IsMusHostingViz() ? switches::kMusHostVizValue : std::string());
     base::CommandLine::ForCurrentProcess()->AppendSwitch(
         switches::kEnableSurfaceSynchronization);
   }
@@ -1480,7 +1478,7 @@ int BrowserMainLoop::BrowserThreadsStarted() {
       BrowserThread::GetTaskRunnerForThread(BrowserThread::IO));
 
   // If mus is not hosting viz, then the browser must.
-  bool browser_is_viz_host = !IsMusHostingViz();
+  bool browser_is_viz_host = !switches::IsMusHostingViz();
 
   bool always_uses_gpu = true;
   bool established_gpu_channel = false;

content/browser/compositor/gpu_process_transport_factory.cc

@@ -60,6 +60,7 @@
 #include "services/service_manager/runner/common/client_util.h"
 #include "services/ui/public/cpp/gpu/context_provider_command_buffer.h"
 #include "third_party/khronos/GLES2/gl2.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/compositor_switches.h"
 #include "ui/compositor/layer.h"
@@ -242,7 +243,7 @@ GpuProcessTransportFactory::CreateSoftwareOutputDevice(
     return base::WrapUnique(new viz::SoftwareOutputDevice);
 
 #if defined(USE_AURA)
-  if (IsMusHostingViz()) {
+  if (switches::IsMusHostingViz()) {
     NOTREACHED();
     return nullptr;
   }

content/browser/gpu/browser_gpu_channel_host_factory.cc

@@ -29,6 +29,7 @@
 #include "gpu/command_buffer/service/gpu_switches.h"
 #include "services/resource_coordinator/public/interfaces/memory_instrumentation/constants.mojom.h"
 #include "services/service_manager/runner/common/client_util.h"
+#include "ui/base/ui_base_switches_util.h"
 
 namespace content {
 
@@ -266,7 +267,7 @@ BrowserGpuChannelHostFactory::AllocateSharedMemory(size_t size) {
 void BrowserGpuChannelHostFactory::EstablishGpuChannel(
     const gpu::GpuChannelEstablishedCallback& callback) {
 #if defined(USE_AURA)
-  DCHECK(!IsMusHostingViz());
+  DCHECK(!switches::IsMusHostingViz());
 #endif
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
   if (gpu_channel_.get() && gpu_channel_->IsLost()) {

content/browser/mus_util.cc

@@ -5,7 +5,6 @@
 #include "content/browser/mus_util.h"
 
 #if defined(USE_AURA)
-#include "content/public/browser/context_factory.h"
 #include "ui/aura/env.h"
 #endif
 
@@ -19,9 +18,4 @@ bool IsUsingMus() {
 #endif
 }
 
-bool IsMusHostingViz() {
-  // TODO(sad): Currently mus always is the viz host.
-  return IsUsingMus();
-}
-
 }  // namespace content

content/browser/mus_util.h

@@ -11,8 +11,6 @@ namespace content {
 
 CONTENT_EXPORT bool IsUsingMus();
 
-bool IsMusHostingViz();
-
 }  // namespace content
 
 #endif  // CONTENT_BROWSER_MUS_UTIL_H_

content/browser/renderer_host/render_widget_host_view_aura.cc

@@ -82,6 +82,7 @@
 #include "ui/base/hit_test.h"
 #include "ui/base/ime/input_method.h"
 #include "ui/base/ui_base_switches.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/compositor/dip_util.h"
@@ -413,7 +414,7 @@ RenderWidgetHostViewAura::RenderWidgetHostViewAura(
       is_guest_view_hack_(is_guest_view_hack),
       device_scale_factor_(0.0f),
       event_handler_(new RenderWidgetHostViewEventHandler(host_, this, this)),
-      frame_sink_id_(IsMusHostingViz()
+      frame_sink_id_(switches::IsMusHostingViz()
                          ? viz::FrameSinkId()
                          : host_->AllocateFrameSinkId(is_guest_view_hack_)),
       weak_ptr_factory_(this) {

content/browser/service_manager/service_manager_context.cc

@@ -24,6 +24,7 @@
 #include "content/browser/browser_main_loop.h"
 #include "content/browser/child_process_launcher.h"
 #include "content/browser/gpu/gpu_process_host.h"
+#include "content/browser/mus_util.h"
 #include "content/browser/service_manager/common_browser_interfaces.h"
 #include "content/browser/utility_process_host_impl.h"
 #include "content/browser/wake_lock/wake_lock_context_host.h"
@@ -65,6 +66,7 @@
 #include "services/video_capture/public/cpp/constants.h"
 #include "services/video_capture/public/interfaces/constants.mojom.h"
 #include "services/viz/public/interfaces/constants.mojom.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/base/ui_features.h"
 
 #if defined(OS_ANDROID)
@@ -250,16 +252,21 @@ std::unique_ptr<service_manager::Service> CreateEmbeddedUIService(
   config.resource_runner = task_runner;
   config.image_cursors_set_weak_ptr = image_cursors_set_weak_ptr;
   config.memory_manager = memory_manager;
+  config.should_host_viz = switches::IsMusHostingViz();
   return base::MakeUnique<ui::Service>(&config);
 }
 
 void RegisterUIServiceInProcessIfNecessary(
     ServiceManagerConnection* connection) {
   // Some tests don't create BrowserMainLoop.
-  if (!base::CommandLine::ForCurrentProcess()->HasSwitch("mus") ||
-      !BrowserMainLoop::GetInstance()) {
+  if (!BrowserMainLoop::GetInstance())
+    return;
+  // Do not embed the UI service when running in mash.
+  if (base::CommandLine::ForCurrentProcess()->HasSwitch("mash"))
+    return;
+  // Do not embed the UI service if not running with --mus.
+  if (!IsUsingMus())
     return;
-  }
 
   service_manager::EmbeddedServiceInfo info;
   info.factory = base::Bind(

content/browser/utility_process_host_impl.cc

@@ -296,6 +296,9 @@ bool UtilityProcessHostImpl::StartProcess() {
       switches::kProxyServer,
 #if defined(OS_MACOSX)
       switches::kEnableSandboxLogging,
+#endif
+#if defined(USE_AURA)
+      switches::kMus,
 #endif
       switches::kUseFakeDeviceForMediaStream,
       switches::kUseFileForFakeVideoCapture,

content/renderer/render_thread_impl.cc

@@ -186,6 +186,7 @@
 #include "third_party/skia/include/core/SkGraphics.h"
 #include "ui/base/layout.h"
 #include "ui/base/ui_base_switches.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/display/display_switches.h"
 #include "ui/gl/gl_switches.h"
 
@@ -330,16 +331,6 @@ void AddHistogramSample(void* hist, int sample) {
   histogram->Add(sample);
 }
 
-bool IsMusHostingViz() {
-#if BUILDFLAG(ENABLE_MUS)
-  const auto* cmdline = base::CommandLine::ForCurrentProcess();
-  return cmdline->GetSwitchValueASCII(switches::kMus) ==
-         switches::kMusHostVizValue;
-#else
-  return false;
-#endif
-}
-
 class FrameFactoryImpl : public mojom::FrameFactory {
  public:
   explicit FrameFactoryImpl(const service_manager::BindSourceInfo& source_info)
@@ -695,10 +686,11 @@ void RenderThreadImpl::Init(
       base::BindRepeating(&CreateSingleSampleMetricsProvider,
                           message_loop()->task_runner(), GetConnector()));
 
-  gpu_ = ui::Gpu::Create(
-      GetConnector(),
-      IsMusHostingViz() ? ui::mojom::kServiceName : mojom::kBrowserServiceName,
-      GetIOTaskRunner());
+  gpu_ =
+      ui::Gpu::Create(GetConnector(),
+                      switches::IsMusHostingViz() ? ui::mojom::kServiceName
+                                                  : mojom::kBrowserServiceName,
+                      GetIOTaskRunner());
 
   viz::mojom::SharedBitmapAllocationNotifierPtr
       shared_bitmap_allocation_notifier_ptr;
@@ -2031,7 +2023,7 @@ void RenderThreadImpl::RequestNewLayerTreeFrameSink(
   }
 
 #if defined(USE_AURA)
-  if (IsMusHostingViz()) {
+  if (switches::IsMusHostingViz()) {
     if (!RendererWindowTreeClient::Get(routing_id)) {
       callback.Run(nullptr);
       return;

content/test/content_test_launcher.cc

@@ -22,6 +22,8 @@
 #include "content/shell/common/shell_switches.h"
 #include "media/base/media_switches.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "ui/base/ui_base_switches.h"
+#include "ui/base/ui_features.h"
 
 #ifdef V8_USE_EXTERNAL_STARTUP_DATA
 #include "gin/v8_initializer.h"
@@ -50,6 +52,12 @@ class ContentBrowserTestSuite : public ContentTestSuiteBase {
  public:
   ContentBrowserTestSuite(int argc, char** argv)
       : ContentTestSuiteBase(argc, argv) {
+#if BUILDFLAG(ENABLE_MUS)
+    // TODO(786453): This should be removed once mus can run without viz.
+    auto* cmd = base::CommandLine::ForCurrentProcess();
+    if (cmd->HasSwitch(switches::kMus))
+      cmd->AppendSwitchASCII(switches::kMus, switches::kMusHostVizValue);
+#endif
   }
   ~ContentBrowserTestSuite() override {}
 

mash/test/mash_test_suite.cc

@@ -16,6 +16,7 @@
 #include "ui/aura/env.h"
 #include "ui/base/resource/resource_bundle.h"
 #include "ui/base/ui_base_paths.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/reflector.h"
 #include "ui/compositor/test/fake_context_factory.h"
@@ -36,6 +37,8 @@ void MashTestSuite::Initialize() {
 
   base::CommandLine::ForCurrentProcess()->AppendSwitch(
       switches::kOverrideUseSoftwareGLForTests);
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kMus, switches::kMusHostVizValue);
 
   // Load ash mus strings and resources; not 'common' (Chrome) resources.
   base::FilePath resources;

services/ui/demo/mus_demo_unittests.cc

@@ -10,6 +10,7 @@
 #include "services/ui/public/interfaces/constants.mojom.h"
 #include "services/ui/public/interfaces/window_server_test.mojom.h"
 #include "testing/gtest/include/gtest/gtest.h"
+#include "ui/base/ui_base_switches.h"
 
 namespace ui {
 namespace demo {
@@ -30,6 +31,8 @@ class MusDemoTest : public service_manager::test::ServiceTest {
 
   void SetUp() override {
     base::CommandLine::ForCurrentProcess()->AppendSwitch("use-test-config");
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
     ServiceTest::SetUp();
   }
 

services/ui/ws/window_server_test_base.cc

@@ -5,6 +5,7 @@
 #include "services/ui/ws/window_server_test_base.h"
 
 #include "base/bind.h"
+#include "base/command_line.h"
 #include "base/location.h"
 #include "base/memory/ptr_util.h"
 #include "base/run_loop.h"
@@ -15,6 +16,7 @@
 #include "ui/aura/env.h"
 #include "ui/aura/mus/window_tree_client.h"
 #include "ui/aura/mus/window_tree_host_mus.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/display/display.h"
 #include "ui/display/display_list.h"
 #include "ui/wm/core/capture_controller.h"
@@ -91,6 +93,8 @@ WindowServerTestBase::ReleaseMostRecentClient() {
 }
 
 void WindowServerTestBase::SetUp() {
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kMus, switches::kMusHostVizValue);
   WindowServerServiceTestBase::SetUp();
 
   env_ = aura::Env::CreateInstance(aura::Env::Mode::MUS);

ui/aura/mus/window_port_mus.cc

@@ -18,6 +18,7 @@
 #include "ui/aura/window_delegate.h"
 #include "ui/aura/window_observer.h"
 #include "ui/base/class_property.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/display/display.h"
 #include "ui/display/screen.h"
 #include "ui/gfx/geometry/dip_util.h"
@@ -591,6 +592,8 @@ void WindowPortMus::UpdatePrimarySurfaceId() {
 }
 
 void WindowPortMus::UpdateClientSurfaceEmbedder() {
+  if (!switches::IsMusHostingViz())
+    return;
   if (window_mus_type() != WindowMusType::TOP_LEVEL_IN_WM &&
       window_mus_type() != WindowMusType::EMBED_IN_OWNER &&
       window_mus_type() != WindowMusType::DISPLAY_MANUALLY_CREATED &&

ui/aura/mus/window_tree_client.cc

@@ -57,6 +57,7 @@
 #include "ui/aura/window_port_for_shutdown.h"
 #include "ui/aura/window_tracker.h"
 #include "ui/base/layout.h"
+#include "ui/base/ui_base_switches_util.h"
 #include "ui/base/ui_base_types.h"
 #include "ui/display/screen.h"
 #include "ui/display/types/display_constants.h"
@@ -224,11 +225,15 @@ WindowTreeClient::WindowTreeClient(
       io_task_runner = io_thread_->task_runner();
     }
 
-    gpu_ = ui::Gpu::Create(connector, ui::mojom::kServiceName, io_task_runner);
-    compositor_context_factory_ =
-        std::make_unique<MusContextFactory>(gpu_.get());
-    initial_context_factory_ = Env::GetInstance()->context_factory();
-    Env::GetInstance()->set_context_factory(compositor_context_factory_.get());
+    if (switches::IsMusHostingViz()) {
+      gpu_ =
+          ui::Gpu::Create(connector, ui::mojom::kServiceName, io_task_runner);
+      compositor_context_factory_ =
+          std::make_unique<MusContextFactory>(gpu_.get());
+      initial_context_factory_ = Env::GetInstance()->context_factory();
+      Env::GetInstance()->set_context_factory(
+          compositor_context_factory_.get());
+    }
 
     // WindowServerTest will create more than one WindowTreeClient. We will not
     // create the discardable memory manager for those tests.

ui/aura/mus/window_tree_client_unittest.cc

@@ -43,6 +43,7 @@
 #include "ui/aura/window_tracker.h"
 #include "ui/aura/window_tree_host_observer.h"
 #include "ui/base/class_property.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/compositor/compositor.h"
 #include "ui/display/display.h"
 #include "ui/display/display_switches.h"
@@ -192,6 +193,8 @@ class WindowTreeClientWmTestSurfaceSync
 
   // WindowTreeClientWmTest:
   void SetUp() override {
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
     if (GetParam()) {
       base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
           switches::kForceDeviceScaleFactor, "2");

ui/aura/test/aura_test_helper.cc

@@ -29,6 +29,7 @@
 #include "ui/base/ime/input_method_factory.h"
 #include "ui/base/ime/input_method_initializer.h"
 #include "ui/base/platform_window_defaults.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/compositor/compositor.h"
 #include "ui/compositor/layer_animator.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
@@ -105,6 +106,11 @@ void AuraTestHelper::SetUp(ui::ContextFactory* context_factory,
   capture_client_ = std::make_unique<client::DefaultCaptureClient>();
   const Env::Mode env_mode =
       (mode_ == Mode::LOCAL) ? Env::Mode::LOCAL : Env::Mode::MUS;
+  if (env_mode == Env::Mode::MUS) {
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kMus, switches::kMusHostVizValue);
+  }
+
   if (mode_ == Mode::MUS_CREATE_WINDOW_TREE_CLIENT)
     InitWindowTreeClient();
   if (!Env::GetInstanceDontCreate())

ui/base/ui_base_switches.cc

@@ -127,7 +127,7 @@ const char kMangleLocalizedStrings[] = "mangle-localized-strings";
 const char kSlowDownCompositingScaleFactor[] =
     "slow-down-compositing-scale-factor";
 
-#if BUILDFLAG(ENABLE_MUS)
+#if defined(USE_AURA)
 // Used to enable the mus service (aka the UI service). This makes mus run in
 // process. It is also used to notify the clients that the UI service is being
 // used. If the value of this flag is set to kMusHostVizValue, then that means

ui/base/ui_base_switches.h

@@ -57,7 +57,7 @@ UI_BASE_EXPORT extern const char kUseSkiaRenderer[];
 UI_BASE_EXPORT extern const char kDisallowNonExactResourceReuse[];
 UI_BASE_EXPORT extern const char kMangleLocalizedStrings[];
 
-#if BUILDFLAG(ENABLE_MUS)
+#if defined(USE_AURA)
 UI_BASE_EXPORT extern const char kMus[];
 UI_BASE_EXPORT extern const char kMusHostVizValue[];
 #endif

ui/base/ui_base_switches_util.cc

@@ -20,4 +20,13 @@ bool IsTouchDragDropEnabled() {
 #endif
 }
 
+bool IsMusHostingViz() {
+#if defined(USE_AURA)
+  auto* cmd = base::CommandLine::ForCurrentProcess();
+  return cmd->GetSwitchValueASCII(switches::kMus) == switches::kMusHostVizValue;
+#else
+  return false;
+#endif
+}
+
 }  // namespace switches

ui/base/ui_base_switches_util.h

@@ -12,6 +12,10 @@ namespace switches {
 UI_BASE_EXPORT bool IsLinkDisambiguationPopupEnabled();
 UI_BASE_EXPORT bool IsTouchDragDropEnabled();
 
+// Returns whether mus is hosting viz. Mus is hosting viz only if --mus flag
+// is set to 'viz'.
+UI_BASE_EXPORT bool IsMusHostingViz();
+
 }  // namespace switches
 
 #endif  // UI_BASE_UI_BASE_SWITCHES_UTIL_H_

ui/views/mus/views_mus_test_suite.cc

@@ -28,6 +28,7 @@
 #include "ui/aura/mus/window_tree_host_mus.h"
 #include "ui/aura/test/mus/input_method_mus_test_api.h"
 #include "ui/aura/window.h"
+#include "ui/base/ui_base_switches.h"
 #include "ui/compositor/test/fake_context_factory.h"
 #include "ui/gl/gl_switches.h"
 #include "ui/views/mus/desktop_window_tree_host_mus.h"
@@ -248,6 +249,8 @@ void ViewsMusTestSuite::Initialize() {
   EnsureCommandLineSwitch(ui::switches::kUseTestConfig);
 
   EnsureCommandLineSwitch(switches::kOverrideUseSoftwareGLForTests);
+  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+      switches::kMus, switches::kMusHostVizValue);
 
   ViewsTestSuite::Initialize();
   service_manager_connections_ = std::make_unique<ServiceManagerConnection>();

ui/wm/test/wm_test_helper.cc

@@ -27,7 +27,8 @@ WMTestHelper::WMTestHelper(const gfx::Size& default_window_size,
                            service_manager::Connector* connector,
                            ui::ContextFactory* context_factory) {
   wm_state_ = std::make_unique<WMState>();
-  aura::Env::GetInstance()->set_context_factory(context_factory);
+  if (context_factory)
+    aura::Env::GetInstance()->set_context_factory(context_factory);
   if (aura::Env::GetInstance()->mode() == aura::Env::Mode::LOCAL)
     InitLocalHost(default_window_size);
   else