Apply RTL transform to the background layer

This is a workaround for views layer bug (458753)

BUG=379777
TEST=maual

Review URL: https://codereview.chromium.org/929653002

Cr-Commit-Position: refs/heads/master@{#316399}

ash/desktop_background/desktop_background_view.cc

@@ -64,6 +64,9 @@ class LayerControlView : public views::View {
     views::View* child = child_at(0);
     child->SetBounds(0, 0, rounded_size.width(), rounded_size.height());
     gfx::Transform transform;
+    // Apply RTL transform explicitly becacuse Views layer code
+    // doesn't handle RTL.  crbug.com/458753.
+    transform.Translate(-child->GetMirroredX(), 0);
     transform.Scale(ui_scale, ui_scale);
     child->SetTransform(transform);
   }