Add FrameGenerator Unit Tests

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) {
-  if (!root_window_->visible())
+  if (!root_window_->visible() ||
+      begin_frame_args.type == cc::BeginFrameArgs::MISSED) {
     return;
+  }
 
   // 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 {
@@ skipping 72 matching lines @@
                bounds_at_origin /* visible_rect */, true /* needs_blending*/,
                window_manager_surface_info_.id(),
                cc::SurfaceDrawQuadType::PRIMARY, nullptr);
 }
 
 void FrameGenerator::SetNeedsBeginFrame(bool needs_begin_frame) {
   if (needs_begin_frame == observing_begin_frames_)
     return;
 
   if (needs_begin_frame) {
+    observing_begin_frames_ = true;

[Fady Samuel, 2017/03/17 14:06:40]

So I was looking at compositor_frame_sink_support.cc and I realized we are a bit
more succinct there. Perhaps this is nicer:

if (needs_begin_frame == observing_begin_frames_)
  return;

observing_begin_frames_ = needs_begin_frame;
if (needs_begin_frame)
  begin_frame_source_->AddObserver(this);
else
  begin_frame_source_->RemoveObserver(this);

[Alex Z., 2017/03/17 14:43:00]

Done.

     begin_frame_source_->AddObserver(this);
-    observing_begin_frames_ = true;
     return;
   }
 
+  observing_begin_frames_ = false;
   begin_frame_source_->RemoveObserver(this);
-  observing_begin_frames_ = false;
 }
 
 }  // namespace ws
 
 }  // namespace ui