cc: Move worker threads to content.

mojo/services/html_viewer/weblayertreeview_impl.cc

 // Copyright 2014 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 "mojo/services/html_viewer/weblayertreeview_impl.h"
 
 #include "base/message_loop/message_loop_proxy.h"
 #include "cc/blink/web_layer_impl.h"
 #include "cc/layers/layer.h"
 #include "cc/output/begin_frame_args.h"
@@ skipping 18 matching lines @@
   main_thread_bound_weak_ptr_ = weak_factory_.GetWeakPtr();
 
   cc::LayerTreeSettings settings;
 
   // For web contents, layer transforms should scale up the contents of layers
   // to keep content always crisp when possible.
   settings.layer_transforms_should_scale_layer_contents = true;
 
   cc::SharedBitmapManager* shared_bitmap_manager = NULL;
   gpu::GpuMemoryBufferManager* gpu_memory_buffer_manager = NULL;
+  cc::TaskGraphRunner* task_graph_runner = NULL;

[jamesr, 2015/03/23 17:55:36]

these 3 should all be nullptr

does this being null mean that mojo html_viewer can't use any worker threads for
raster? what would need to be implemented for it to do so?

[reveman, 2015/03/23 18:39:46]

https://codereview.chromium.org/1023813004
Yes, we'd have to create a TaskGraphRunner instance and at least 1 worker thread
to process tasks. A simple example can be found in the
content/browser/compositor/gpu_process_transport_factory.cc change of this
patch.

We would also need a SharedBitmapManager and/or a GpuMemoryBufferManager
instance to perform non-GPU raster. SharedBitmaps for sw compositing,
GpuMemoryBuffer for hw compositing.

 
   layer_tree_host_ =
       cc::LayerTreeHost::CreateThreaded(this,
                                         shared_bitmap_manager,
                                         gpu_memory_buffer_manager,
+                                        task_graph_runner,
                                         settings,
                                         base::MessageLoopProxy::current(),
                                         compositor_message_loop_proxy,
                                         nullptr);
   DCHECK(layer_tree_host_);
 
   if (surface && gpu_service) {
     mojo::CommandBufferPtr cb;
     gpu_service->CreateOffscreenGLES2Context(GetProxy(&cb));
     scoped_refptr<cc::ContextProvider> context_provider(
@@ skipping 189 matching lines @@
       base::Bind(&WebLayerTreeViewImpl::DidCreateSurfaceOnMainThread,
                  main_thread_bound_weak_ptr_,
                  id));
 }
 
 void WebLayerTreeViewImpl::DidCreateSurfaceOnMainThread(cc::SurfaceId id) {
   view_->SetSurfaceId(mojo::SurfaceId::From(id));
 }
 
 }  // namespace html_viewer