Convert //ash from scoped_ptr to std::unique_ptr

ash/host/transformer_helper.cc

Index: ash/host/transformer_helper.cc
diff --git a/ash/host/transformer_helper.cc b/ash/host/transformer_helper.cc
index aba946053814031271959e57c01624c511824801..7355b0f051ddb2dcac239aa40ae3145137c6be50 100644
--- a/ash/host/transformer_helper.cc
+++ b/ash/host/transformer_helper.cc
@@ -73,13 +73,14 @@ gfx::Insets TransformerHelper::GetHostInsets() const {
 }
 
 void TransformerHelper::SetTransform(const gfx::Transform& transform) {
-  scoped_ptr<RootWindowTransformer> transformer(new SimpleRootWindowTransformer(
-      ash_host_->AsWindowTreeHost()->window(), transform));
+  std::unique_ptr<RootWindowTransformer> transformer(
+      new SimpleRootWindowTransformer(ash_host_->AsWindowTreeHost()->window(),
+                                      transform));
   SetRootWindowTransformer(std::move(transformer));
 }
 
 void TransformerHelper::SetRootWindowTransformer(
-    scoped_ptr<RootWindowTransformer> transformer) {
+    std::unique_ptr<RootWindowTransformer> transformer) {
   transformer_ = std::move(transformer);
   aura::WindowTreeHost* host = ash_host_->AsWindowTreeHost();
   aura::Window* window = host->window();