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

blimp/client/support/compositor/blimp_embedder_compositor.cc

Index: blimp/client/support/compositor/blimp_embedder_compositor.cc
diff --git a/blimp/client/support/compositor/blimp_embedder_compositor.cc b/blimp/client/support/compositor/blimp_embedder_compositor.cc
index f8116dced4d77d54370a5aa925b4dfe935741825..da0e4c8d7b9febbabc28e1ce14549f7055eb69b5 100644
--- a/blimp/client/support/compositor/blimp_embedder_compositor.cc
+++ b/blimp/client/support/compositor/blimp_embedder_compositor.cc
@@ -51,6 +51,9 @@ class DisplayOutputSurface : public cc::OutputSurface {
   ~DisplayOutputSurface() override = default;
 
   // cc::OutputSurface implementation
+  void BindToClient(cc::OutputSurfaceClient* client) override {
+    client_ = client;
+  }
   void EnsureBackbuffer() override {}
   void DiscardBackbuffer() override {
     context_provider()->ContextGL()->DiscardBackbufferCHROMIUM();
@@ -90,6 +93,7 @@ class DisplayOutputSurface : public cc::OutputSurface {
  private:
   void SwapBuffersCallback() { client_->DidReceiveSwapBuffersAck(); }
 
+  cc::OutputSurfaceClient* client_ = nullptr;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   base::WeakPtrFactory<DisplayOutputSurface> weak_ptr_factory_;