Introduce ViewRoot forwarding input/view events to native

blimp/client/core/contents/blimp_contents_view_impl_android.cc

Index: blimp/client/core/contents/blimp_contents_view_impl_android.cc
diff --git a/blimp/client/core/contents/blimp_contents_view_impl_android.cc b/blimp/client/core/contents/blimp_contents_view_impl_android.cc
index 6205fbd40ef86adac9f56d0746360e935977a3cd..992032647d9afe953c837fb8903b7a708dc8914b 100644
--- a/blimp/client/core/contents/blimp_contents_view_impl_android.cc
+++ b/blimp/client/core/contents/blimp_contents_view_impl_android.cc
@@ -32,7 +32,10 @@ BlimpContentsViewImplAndroid::BlimpContentsViewImplAndroid(
   view_ = base::MakeUnique<ui::ViewAndroid>();
   view_->SetDelegate(blimp_view_->CreateViewAndroidDelegate());
   view_->SetLayer(contents_layer);
-  blimp_contents->GetNativeWindow()->AddChild(view_.get());
+
+  view_root_ = base::MakeUnique<ui::ViewRoot>();
+  view_root_->AddChild(view_.get());
+  view_root_->SetWindowAndroid(blimp_contents->GetNativeWindow());
 }
 
 BlimpContentsViewImplAndroid::~BlimpContentsViewImplAndroid() = default;