cc: Make OutputSurface::BindToClient pure virtual and not return bool

services/ui/surfaces/direct_output_surface.h

Index: services/ui/surfaces/direct_output_surface.h
diff --git a/services/ui/surfaces/direct_output_surface.h b/services/ui/surfaces/direct_output_surface.h
index 4d95bbac9fe5878bc5273d3e9585905104bd2d5c..98c09d69004439dd6b57dc6da079db96677b74db 100644
--- a/services/ui/surfaces/direct_output_surface.h
+++ b/services/ui/surfaces/direct_output_surface.h
@@ -29,7 +29,7 @@ class DirectOutputSurface : public cc::OutputSurface,
   ~DirectOutputSurface() override;
 
   // cc::OutputSurface implementation
-  bool BindToClient(cc::OutputSurfaceClient* client) override;
+  void BindToClient(cc::OutputSurfaceClient* client) override;
   void EnsureBackbuffer() override;
   void DiscardBackbuffer() override;
   void BindFramebuffer() override;
@@ -53,6 +53,7 @@ class DirectOutputSurface : public cc::OutputSurface,
  private:
   void OnSwapBuffersComplete();
 
+  cc::OutputSurfaceClient* client_ = nullptr;
   cc::SyntheticBeginFrameSource* const synthetic_begin_frame_source_;
   base::WeakPtrFactory<DirectOutputSurface> weak_ptr_factory_;
 };