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

blimp/client/support/compositor/blimp_embedder_compositor.cc

 // Copyright 2016 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 "blimp/client/support/compositor/blimp_embedder_compositor.h"
 
 #include "base/bind.h"
 #include "base/lazy_instance.h"
 #include "base/memory/weak_ptr.h"
 #include "base/threading/thread_task_runner_handle.h"
@@ skipping 33 matching lines @@
   explicit DisplayOutputSurface(
       scoped_refptr<cc::ContextProvider> context_provider,
       scoped_refptr<base::SingleThreadTaskRunner> task_runner)
       : cc::OutputSurface(std::move(context_provider)),
         task_runner_(std::move(task_runner)),
         weak_ptr_factory_(this) {}
 
   ~DisplayOutputSurface() override = default;
 
   // cc::OutputSurface implementation
+  void BindToClient(cc::OutputSurfaceClient* client) override {
+    client_ = client;
+  }
   void EnsureBackbuffer() override {}
   void DiscardBackbuffer() override {
     context_provider()->ContextGL()->DiscardBackbufferCHROMIUM();
   }
   void BindFramebuffer() override {
     context_provider()->ContextGL()->BindFramebuffer(GL_FRAMEBUFFER, 0);
   }
   void Reshape(const gfx::Size& size,
                float device_scale_factor,
                const gfx::ColorSpace& color_space,
@@ skipping 19 matching lines @@
     // We assume we have an alpha channel from the BlimpContextProvider, so use
     // GL_RGBA here.
     return GL_RGBA;
   }
   bool HasExternalStencilTest() const override { return false; }
   void ApplyExternalStencil() override {}
 
  private:
   void SwapBuffersCallback() { client_->DidReceiveSwapBuffersAck(); }
 
+  cc::OutputSurfaceClient* client_ = nullptr;
   scoped_refptr<base::SingleThreadTaskRunner> task_runner_;
   base::WeakPtrFactory<DisplayOutputSurface> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(DisplayOutputSurface);
 };
 
 base::LazyInstance<SimpleTaskGraphRunner> g_task_graph_runner =
     LAZY_INSTANCE_INITIALIZER;
 
 }  // namespace
@@ skipping 83 matching lines @@
   NOTREACHED() << "Can't fail to initialize the CompositorFrameSink here";
 }
 
 void BlimpEmbedderCompositor::HandlePendingCompositorFrameSinkRequest() {
   DCHECK(compositor_frame_sink_request_pending_);
 
   // Can't handle the request right now since we don't have a widget.
   if (!host_->IsVisible())
     return;
 
   DCHECK(context_provider_);

[Khushal, 2016/10/25 01:10:02]

Should we context_provider_->BindToCurrentThread() here and DCHECK that it was
successful? Since otherwise its going to fail later anyway?

[danakj, 2016/10/25 18:58:38]

No this is for the layer compositor's context it will be used on the compositor
thread, so we must bind it there (we do so inside LTHI).

[danakj, 2016/10/25 19:00:00]

I lied, I guess this is shared. Blimp is single threaded on the client? I didn't
realize. Anyhow.. ya it needs to be bound before being given to the Display.

[Khushal, 2016/10/25 20:45:06]

I actually got confused about whether it was needed because I saw you did a Bind
in CompositorImpl before giving the context to the Display. I guess you had to
do it there to query the gpu::Capabilities?
Nope, the compositor which is the equivalent of the renderer compositor is
BlimpCompositor, which is threaded.

This one is meant to be a cheap knock off of the UI compositor in Chrome, so
anyone who embeds Blimp always gets a cc::Layer as the output, and Chrome adds
that to the UI compositor's LayerTree. So when we had to make the standalone app
a Blimp embedder also, we just added this to do what the Chrome UI compositor
would do.

[danakj, 2016/10/25 20:47:23]

Ya, Display will no longer (double) bind the context. GPTF does a bind, and I
added a bind here as you suggested because nothing would bind it now until it
went to LTHI which is late.

 
   gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager =
       compositor_dependencies_->GetGpuMemoryBufferManager();
 
   auto task_runner = base::ThreadTaskRunnerHandle::Get();
   auto display_output_surface =
       base::MakeUnique<DisplayOutputSurface>(context_provider_, task_runner);
 
   std::unique_ptr<cc::SyntheticBeginFrameSource> begin_frame_source(
       new cc::DelayBasedBeginFrameSource(
@@ skipping 13 matching lines @@
   // The Browser compositor and display share the same context provider.
   auto compositor_frame_sink = base::MakeUnique<cc::DirectCompositorFrameSink>(
       frame_sink_id_, compositor_dependencies_->GetSurfaceManager(),
       display_.get(), context_provider_, nullptr);
 
   host_->SetCompositorFrameSink(std::move(compositor_frame_sink));
 }
 
 }  // namespace client
 }  // namespace blimp