services/ui: Inject GpuService instance where needed, instead of singleton.

services/ui/public/cpp/output_surface.h

Index: services/ui/public/cpp/output_surface.h
diff --git a/services/ui/public/cpp/output_surface.h b/services/ui/public/cpp/output_surface.h
index fb38073b39625d9ecf0f81237d4150143d87c3b2..1d3c560410b0c87c281cf1be88121336c0d2f018 100644
--- a/services/ui/public/cpp/output_surface.h
+++ b/services/ui/public/cpp/output_surface.h
@@ -14,9 +14,12 @@
 
 namespace ui {
 
+class GpuService;
+
 class OutputSurface : public cc::OutputSurface, public WindowSurfaceClient {
  public:
-  explicit OutputSurface(std::unique_ptr<WindowSurface> surface);
+  OutputSurface(GpuService* gpu_service,
+                std::unique_ptr<WindowSurface> surface);
   ~OutputSurface() override;
 
   // cc::OutputSurface implementation.