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

cc/test/pixel_test_output_surface.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/test/pixel_test_output_surface.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 11 matching lines @@
     : OutputSurface(std::move(context_provider)), weak_ptr_factory_(this) {
   capabilities_.flipped_output_surface = flipped_output_surface;
 }
 
 PixelTestOutputSurface::PixelTestOutputSurface(
     std::unique_ptr<SoftwareOutputDevice> software_device)
     : OutputSurface(std::move(software_device)), weak_ptr_factory_(this) {}
 
 PixelTestOutputSurface::~PixelTestOutputSurface() = default;
 
+void PixelTestOutputSurface::BindToClient(OutputSurfaceClient* client) {
+  client_ = client;
+}
+
 void PixelTestOutputSurface::EnsureBackbuffer() {}
 
 void PixelTestOutputSurface::DiscardBackbuffer() {}
 
 void PixelTestOutputSurface::BindFramebuffer() {
   context_provider()->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER, 0);
 }
 
 void PixelTestOutputSurface::Reshape(const gfx::Size& size,
                                      float device_scale_factor,
@@ skipping 41 matching lines @@
 }
 
 uint32_t PixelTestOutputSurface::GetFramebufferCopyTextureFormat() {
   // This format will work if the |context_provider| has an RGB or RGBA
   // framebuffer. For now assume tests do not want/care about alpha in
   // the root render pass.
   return GL_RGB;
 }
 
 }  // namespace cc