[cc] Fix CompositorFrameSinkSupport BeginFrameAck interface.

services/ui/ws/frame_generator.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 "services/ui/ws/frame_generator.h"
 
 #include <utility>
 #include <vector>
 
 #include "cc/output/compositor_frame.h"
@@ skipping 75 matching lines @@
                             const gfx::Rect& viewport,
                             bool resourceless_software_draw) {}
 
 void FrameGenerator::SetMemoryPolicy(const cc::ManagedMemoryPolicy& policy) {}
 
 void FrameGenerator::SetExternalTilePriorityConstraints(
     const gfx::Rect& viewport_rect,
     const gfx::Transform& transform) {}
 
 void FrameGenerator::OnBeginFrame(const cc::BeginFrameArgs& begin_frame_args) {
+  // TODO(eseckler): Acknowledge BeginFrame if we don't submit CompositorFrame.

[Fady Samuel, 2017/03/18 13:03:11]

Some unit tests have been introduced for FrameGenerator. They might fail unless
you do this now?

[Eric Seckler, 2017/03/20 11:54:03]

Since it doesn't ack any BeginFrames at the moment, I don't think any existing
tests should be failing as a result of this added todo.

Let me fix this separately and add a test for the acks in FrameGenerator at the
same time :)

   if (!root_window_->visible())
     return;
+  last_begin_frame_args_ = begin_frame_args;
 
   // TODO(fsamuel): We should add a trace for generating a top level frame.
   cc::CompositorFrame frame(GenerateCompositorFrame(root_window_->bounds()));
 
   compositor_frame_sink_->SubmitCompositorFrame(std::move(frame));
   SetNeedsBeginFrame(false);
-  last_begin_frame_args_ = begin_frame_args;
 }
 
 const cc::BeginFrameArgs& FrameGenerator::LastUsedBeginFrameArgs() const {
   return last_begin_frame_args_;
 }
 
 void FrameGenerator::OnBeginFrameSourcePausedChanged(bool paused) {}
 
 cc::CompositorFrame FrameGenerator::GenerateCompositorFrame(
     const gfx::Rect& output_rect) {
@@ skipping 20 matching lines @@
     render_pass->filters.Append(cc::FilterOperation::CreateInvertFilter(1.f));
     quad->SetNew(shared_state, output_rect, output_rect, render_pass_id,
                  0 /* mask_resource_id */, gfx::RectF() /* mask_uv_rect */,
                  gfx::Size() /* mask_texture_size */,
                  gfx::Vector2dF() /* filters_scale */,
                  gfx::PointF() /* filters_origin */,
                  gfx::RectF() /* tex_coord_rect */);
     frame.render_pass_list.push_back(std::move(invert_pass));
   }
   frame.metadata.device_scale_factor = device_scale_factor_;
+  frame.metadata.begin_frame_ack = cc::BeginFrameAck(
+      last_begin_frame_args_.source_id, last_begin_frame_args_.sequence_number,
+      last_begin_frame_args_.sequence_number, 0, true);
 
   if (window_manager_surface_info_.is_valid()) {
     frame.metadata.referenced_surfaces.push_back(
         window_manager_surface_info_.id());
   }
 
   return frame;
 }
 
 void FrameGenerator::DrawWindow(cc::RenderPass* pass) {
@@ skipping 37 matching lines @@
     return;
   }
 
   begin_frame_source_->RemoveObserver(this);
   observing_begin_frames_ = false;
 }
 
 }  // namespace ws
 
 }  // namespace ui