Makes tests either use mock compositor or mock WebGraphicsContext3D

ui/aura/desktop.cc

Index: ui/aura/desktop.cc
diff --git a/ui/aura/desktop.cc b/ui/aura/desktop.cc
index 38818e69f46b9ae7776eb9f29d2b8a256da85d82..c3256f69738e816486d21ca6beb9e494b71efe79 100644
--- a/ui/aura/desktop.cc
+++ b/ui/aura/desktop.cc
@@ -415,23 +415,21 @@ Desktop::Desktop()
   host_->SetDesktop(this);
   last_mouse_location_ = host_->QueryMouseLocation();
 
-  if (ui::Compositor::compositor_factory()) {
-    compositor_ = (*ui::Compositor::compositor_factory())(this);
-  } else {
 #ifdef USE_WEBKIT_COMPOSITOR
-    ui::CompositorCC::Initialize(false);
+  ui::CompositorCC::Initialize(false);
 #endif
-    compositor_ = ui::Compositor::Create(this, host_->GetAcceleratedWidget(),
-                                         host_->GetSize());
-  }
+  compositor_ = ui::Compositor::Create(this, host_->GetAcceleratedWidget(),
+                                       host_->GetSize());
   DCHECK(compositor_.get());
 }
 
 Desktop::~Desktop() {
   in_destructor_ = true;
+  // Make sure to NULL out the compositor before terminating so that state is
+  // cleared and we don't hit asserts.
+  compositor_ = NULL;
 #ifdef USE_WEBKIT_COMPOSITOR
-  if (!ui::Compositor::compositor_factory())
-    ui::CompositorCC::Terminate();
+  ui::CompositorCC::Terminate();
 #endif
   if (instance_ == this)
     instance_ = NULL;