p1 mus+ash chrome renders ui and content

ui/views/mus/native_widget_mus.cc

Index: ui/views/mus/native_widget_mus.cc
diff --git a/ui/views/mus/native_widget_mus.cc b/ui/views/mus/native_widget_mus.cc
index 578c9ea19810f9a6102a0c176fdfe3b9fc5e7619..70245bcc03a6793c991977720d836363901e078c 100644
--- a/ui/views/mus/native_widget_mus.cc
+++ b/ui/views/mus/native_widget_mus.cc
@@ -259,13 +259,15 @@ void NativeWidgetMus::InitNativeWidget(const Widget::InitParams& params) {
   // picked up.
   ui::ContextFactory* default_context_factory =
       aura::Env::GetInstance()->context_factory();
-  aura::Env::GetInstance()->set_context_factory(context_factory_.get());
+  // For Chrome, we need the GpuProcessTransportFactory so that renderer and
+  // browser pixels are composited into a single backing
+  // SoftwareOutputDeviceMus.
+  if (!default_context_factory)
+    aura::Env::GetInstance()->set_context_factory(context_factory_.get());
   window_tree_host_.reset(
       new WindowTreeHostMus(shell_, this, window_, surface_type_));
   window_tree_host_->InitHost();
   aura::Env::GetInstance()->set_context_factory(default_context_factory);
-  DCHECK_EQ(context_factory_.get(),
-            window_tree_host_->compositor()->context_factory());
 
   focus_client_.reset(new wm::FocusController(new FocusRulesImpl));