[cc] Add a way to control the compositor's BeginFrames externally.

Exposes a setting and an interface for enabling externally-controlled
BeginFrames in ui::Compositor and adds a command line flag for the
full-pipeline scheduling mode.

Bug: 646774
Cq-Include-Trybots: master.tryserver.blink:linux_trusty_blink_rel;master.tryserver.chromium.linux:linux_site_isolation
Change-Id: I923b5ab66652c65c1384b9fe5075c0a427559fc6
Reviewed-on: https://chromium-review.googlesource.com/558252
Commit-Queue: Eric Seckler <eseckler@chromium.org>
Reviewed-by: Fady Samuel <fsamuel@chromium.org>
Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Sunny Sachanandani <sunnyps@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490719}

cc/base/switches.cc

@@ -49,6 +49,11 @@ const char kEnableTileCompression[] = "enable-tile-compression";
 // Enables the GPU benchmarking extension
 const char kEnableGpuBenchmarking[] = "enable-gpu-benchmarking";
 
+// Effectively disables pipelining of compositor frame production stages by
+// waiting for each stage to finish before completing a frame.
+const char kRunAllCompositorStagesBeforeDraw[] =
+    "run-all-compositor-stages-before-draw";
+
 // Renders a border around compositor layers to help debug and study
 // layer compositing.
 const char kShowCompositedLayerBorders[] = "show-composited-layer-borders";

cc/base/switches.h

@@ -30,6 +30,7 @@ CC_BASE_EXPORT extern const char kEnableTileCompression[];
 
 // Switches for both the renderer and ui compositors.
 CC_BASE_EXPORT extern const char kEnableGpuBenchmarking[];
+CC_BASE_EXPORT extern const char kRunAllCompositorStagesBeforeDraw[];
 
 // Debug visualizations.
 CC_BASE_EXPORT extern const char kShowCompositedLayerBorders[];

cc/trees/layer_tree_settings.cc

@@ -35,6 +35,8 @@ SchedulerSettings LayerTreeSettings::ToSchedulerSettings() const {
   scheduler_settings.enable_latency_recovery = enable_latency_recovery;
   scheduler_settings.background_frame_interval =
       base::TimeDelta::FromSecondsD(1.0 / background_animation_rate);
+  scheduler_settings.wait_for_all_pipeline_stages_before_draw =
+      wait_for_all_pipeline_stages_before_draw;
   return scheduler_settings;
 }
 

cc/trees/layer_tree_settings.h

@@ -115,6 +115,12 @@ class CC_EXPORT LayerTreeSettings {
   // in ResourcePool. Only used for layout or pixel tests, as non-deterministic
   // resource sizes can lead to floating point error and noise in these tests.
   bool disallow_non_exact_resource_reuse = false;
+
+  // Whether the Scheduler should wait for all pipeline stages before attempting
+  // to draw. If |true|, they will block indefinitely until all stages have
+  // completed the current BeginFrame before triggering their own BeginFrame
+  // deadlines.
+  bool wait_for_all_pipeline_stages_before_draw = false;
 };
 
 }  // namespace cc

components/viz/service/display/display.cc

@@ -95,6 +95,14 @@ void Display::Initialize(DisplayClient* client,
   }
 }
 
+void Display::AddObserver(DisplayObserver* observer) {
+  observers_.AddObserver(observer);
+}
+
+void Display::RemoveObserver(DisplayObserver* observer) {
+  observers_.RemoveObserver(observer);
+}
+
 void Display::SetLocalSurfaceId(const LocalSurfaceId& id,
                                 float device_scale_factor) {
   if (current_surface_id_.local_surface_id() == id &&
@@ -422,6 +430,11 @@ bool Display::SurfaceHasUndrawnFrame(const SurfaceId& surface_id) const {
   return surface->HasUndrawnActiveFrame();
 }
 
+void Display::DidFinishFrame(const BeginFrameAck& ack) {
+  for (auto& observer : observers_)
+    observer.OnDisplayDidFinishFrame(ack);
+}
+
 const SurfaceId& Display::CurrentSurfaceId() {
   return current_surface_id_;
 }

components/viz/service/display/display.h

@@ -9,6 +9,7 @@
 #include <vector>
 
 #include "base/macros.h"
+#include "base/observer_list.h"
 #include "cc/output/output_surface_client.h"
 #include "components/viz/common/frame_sinks/begin_frame_source.h"
 #include "components/viz/common/resources/returned_resource.h"
@@ -44,6 +45,13 @@ namespace viz {
 class DisplayClient;
 class SharedBitmapManager;
 
+class VIZ_SERVICE_EXPORT DisplayObserver {
+ public:
+  virtual ~DisplayObserver() {}
+
+  virtual void OnDisplayDidFinishFrame(const BeginFrameAck& ack) = 0;
+};
+
 // A Display produces a surface that can be used to draw to a physical display
 // (OutputSurface). The client is responsible for creating and sizing the
 // surface IDs used to draw into the display and deciding when to draw.
@@ -64,6 +72,9 @@ class VIZ_SERVICE_EXPORT Display : public DisplaySchedulerClient,
 
   void Initialize(DisplayClient* client, SurfaceManager* surface_manager);
 
+  void AddObserver(DisplayObserver* observer);
+  void RemoveObserver(DisplayObserver* observer);
+
   // device_scale_factor is used to communicate to the external window system
   // what scale this was rendered at.
   void SetLocalSurfaceId(const LocalSurfaceId& id, float device_scale_factor);
@@ -81,6 +92,7 @@ class VIZ_SERVICE_EXPORT Display : public DisplaySchedulerClient,
   bool SurfaceDamaged(const SurfaceId& surface_id,
                       const BeginFrameAck& ack) override;
   void SurfaceDiscarded(const SurfaceId& surface_id) override;
+  void DidFinishFrame(const BeginFrameAck& ack) override;
 
   // OutputSurfaceClient implementation.
   void SetNeedsRedrawRect(const gfx::Rect& damage_rect) override;
@@ -106,6 +118,7 @@ class VIZ_SERVICE_EXPORT Display : public DisplaySchedulerClient,
   const RendererSettings settings_;
 
   DisplayClient* client_ = nullptr;
+  base::ObserverList<DisplayObserver> observers_;
   SurfaceManager* surface_manager_ = nullptr;
   const FrameSinkId frame_sink_id_;
   SurfaceId current_surface_id_;

components/viz/service/display/display_scheduler.cc

@@ -471,8 +471,11 @@ void DisplayScheduler::OnBeginFrameDeadline() {
 
 void DisplayScheduler::DidFinishFrame(bool did_draw) {
   DCHECK(begin_frame_source_);
-  // TODO(eseckler): Let client know that frame was completed.
   begin_frame_source_->DidFinishFrame(this);
+
+  BeginFrameAck ack(current_begin_frame_args_.source_id,
+                    current_begin_frame_args_.sequence_number, did_draw);
+  client_->DidFinishFrame(ack);
 }
 
 void DisplayScheduler::DidSwapBuffers() {

components/viz/service/display/display_scheduler.h

@@ -32,6 +32,7 @@ class VIZ_SERVICE_EXPORT DisplaySchedulerClient {
   virtual bool SurfaceDamaged(const SurfaceId& surface_id,
                               const BeginFrameAck& ack) = 0;
   virtual void SurfaceDiscarded(const SurfaceId& surface_id) = 0;
+  virtual void DidFinishFrame(const BeginFrameAck& ack) = 0;
 };
 
 class VIZ_SERVICE_EXPORT DisplayScheduler : public BeginFrameObserverBase,

components/viz/service/display/display_scheduler_unittest.cc

@@ -13,6 +13,7 @@
 #include "components/viz/common/frame_sinks/begin_frame_args.h"
 #include "components/viz/common/surfaces/surface_info.h"
 #include "components/viz/service/display/display.h"
+#include "components/viz/test/begin_frame_args_test.h"
 #include "components/viz/test/fake_external_begin_frame_source.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
@@ -52,6 +53,10 @@ class FakeDisplaySchedulerClient : public DisplaySchedulerClient {
 
   void SurfaceDiscarded(const SurfaceId& surface_id) override {}
 
+  void DidFinishFrame(const BeginFrameAck& ack) override {
+    last_begin_frame_ack_ = ack;
+  }
+
   int draw_and_swap_count() const { return draw_and_swap_count_; }
 
   void SetNextDrawAndSwapFails() { next_draw_and_swap_fails_ = true; }
@@ -60,10 +65,13 @@ class FakeDisplaySchedulerClient : public DisplaySchedulerClient {
     undrawn_surfaces_.insert(surface_id);
   }
 
+  const BeginFrameAck& last_begin_frame_ack() { return last_begin_frame_ack_; }
+
  protected:
   int draw_and_swap_count_;
   bool next_draw_and_swap_fails_;
   std::set<SurfaceId> undrawn_surfaces_;
+  BeginFrameAck last_begin_frame_ack_;
 };
 
 class TestDisplayScheduler : public DisplayScheduler {
@@ -261,9 +269,11 @@ TEST_F(DisplaySchedulerTest, SurfaceDamaged) {
 
   scheduler_.SetVisible(true);
   scheduler_.SetNewRootSurface(root_surface_id);
+  EXPECT_EQ(BeginFrameAck(), client_.last_begin_frame_ack());
 
   // Set surface1 as active via SurfaceDamageExpected().
   AdvanceTimeAndBeginFrameForTest({sid1});
+  EXPECT_EQ(BeginFrameAck(), client_.last_begin_frame_ack());
 
   // Damage only from surface 2 (inactive) does not trigger deadline early.
   SurfaceDamaged(sid2);
@@ -277,6 +287,9 @@ TEST_F(DisplaySchedulerTest, SurfaceDamaged) {
   EXPECT_GE(now_src().NowTicks(),
             scheduler_.DesiredBeginFrameDeadlineTimeForTest());
   scheduler_.BeginFrameDeadlineForTest();
+  EXPECT_EQ(BeginFrameAck(last_begin_frame_args_.source_id,
+                          last_begin_frame_args_.sequence_number, true),
+            client_.last_begin_frame_ack());
 
   // Set both surface 1 and 2 as active via SurfaceDamageExpected().
   AdvanceTimeAndBeginFrameForTest({sid1, sid2});
@@ -291,6 +304,9 @@ TEST_F(DisplaySchedulerTest, SurfaceDamaged) {
   EXPECT_GE(now_src().NowTicks(),
             scheduler_.DesiredBeginFrameDeadlineTimeForTest());
   scheduler_.BeginFrameDeadlineForTest();
+  EXPECT_EQ(BeginFrameAck(last_begin_frame_args_.source_id,
+                          last_begin_frame_args_.sequence_number, true),
+            client_.last_begin_frame_ack());
 
   // Surface damage with |!has_damage| triggers early deadline if other damage
   // exists.
@@ -318,6 +334,9 @@ TEST_F(DisplaySchedulerTest, SurfaceDamaged) {
   EXPECT_LT(now_src().NowTicks(),
             scheduler_.DesiredBeginFrameDeadlineTimeForTest());
   scheduler_.BeginFrameDeadlineForTest();
+  EXPECT_EQ(BeginFrameAck(last_begin_frame_args_.source_id,
+                          last_begin_frame_args_.sequence_number, false),
+            client_.last_begin_frame_ack());
 
   // System should be idle now.
   AdvanceTimeAndBeginFrameForTest(std::vector<SurfaceId>());

content/browser/compositor/gpu_process_transport_factory.cc

@@ -24,6 +24,7 @@
 #include "cc/output/vulkan_in_process_context_provider.h"
 #include "cc/raster/single_thread_task_graph_runner.h"
 #include "cc/raster/task_graph_runner.h"
+#include "components/viz/common/frame_sinks/begin_frame_args.h"
 #include "components/viz/common/frame_sinks/begin_frame_source.h"
 #include "components/viz/common/frame_sinks/delay_based_time_source.h"
 #include "components/viz/common/gl_helper.h"
@@ -186,13 +187,44 @@ bool IsCALayersDisabledFromCommandLine() {
 
 namespace content {
 
+class ExternalBeginFrameController : public viz::ExternalBeginFrameSourceClient,
+                                     public viz::DisplayObserver {
+ public:
+  explicit ExternalBeginFrameController(ui::Compositor* compositor)
+      : begin_frame_source_(this), compositor_(compositor) {}
+  ~ExternalBeginFrameController() override {}
+
+  // Issue a BeginFrame with the given |args|.
+  void IssueExternalBeginFrame(const viz::BeginFrameArgs& args) {
+    begin_frame_source_.OnBeginFrame(args);
+  }
+
+  viz::BeginFrameSource* begin_frame_source() { return &begin_frame_source_; }
+
+ private:
+  // viz::ExternalBeginFrameSourceClient implementation.
+  void OnNeedsBeginFrames(bool needs_begin_frames) override {
+    compositor_->OnNeedsExternalBeginFrames(needs_begin_frames);
+  }
+
+  // viz::DisplayObserver implementation.
+  void OnDisplayDidFinishFrame(const viz::BeginFrameAck& ack) override {
+    compositor_->OnDisplayDidFinishFrame(ack);
+  }
+
+  viz::ExternalBeginFrameSource begin_frame_source_;
+  ui::Compositor* compositor_ = nullptr;
+};
+
 struct GpuProcessTransportFactory::PerCompositorData {
   gpu::SurfaceHandle surface_handle = gpu::kNullSurfaceHandle;
   BrowserCompositorOutputSurface* display_output_surface = nullptr;
-  // Either |synthetic_begin_frame_source| or |gpu_vsync_begin_frame_source| is
-  // valid but not both at the same time.
+  // Exactly one of |synthetic_begin_frame_source|,
+  // |gpu_vsync_begin_frame_source|, and |external_begin_frame_source| is valid
+  // at the same time.
   std::unique_ptr<viz::SyntheticBeginFrameSource> synthetic_begin_frame_source;
   std::unique_ptr<GpuVSyncBeginFrameSource> gpu_vsync_begin_frame_source;
+  std::unique_ptr<ExternalBeginFrameController> external_begin_frame_controller;
   ReflectorImpl* reflector = nullptr;
   std::unique_ptr<viz::Display> display;
   bool output_is_secure = false;
@@ -220,6 +252,9 @@ GpuProcessTransportFactory::GpuProcessTransportFactory(
     }
   }
 
+  if (command_line->HasSwitch(cc::switches::kRunAllCompositorStagesBeforeDraw))
+    wait_for_all_pipeline_stages_before_draw_ = true;
+
   task_graph_runner_->Start("CompositorTileWorker1",
                             base::SimpleThread::Options());
 #if defined(OS_WIN)
@@ -486,7 +521,6 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
 
   BrowserCompositorOutputSurface::UpdateVSyncParametersCallback vsync_callback =
       base::Bind(&ui::Compositor::SetDisplayVSyncParameters, compositor);
-  viz::BeginFrameSource* begin_frame_source = nullptr;
   GpuVSyncControl* gpu_vsync_control = nullptr;
 
   std::unique_ptr<BrowserCompositorOutputSurface> display_output_surface;
@@ -560,9 +594,14 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
 
   std::unique_ptr<viz::SyntheticBeginFrameSource> synthetic_begin_frame_source;
   std::unique_ptr<GpuVSyncBeginFrameSource> gpu_vsync_begin_frame_source;
+  std::unique_ptr<ExternalBeginFrameController> external_begin_frame_controller;
 
-  if (!begin_frame_source) {
-    if (!disable_display_vsync_) {
+  viz::BeginFrameSource* begin_frame_source = nullptr;
+  if (compositor->external_begin_frames_enabled()) {
+    external_begin_frame_controller =
+        base::MakeUnique<ExternalBeginFrameController>(compositor.get());
+    begin_frame_source = external_begin_frame_controller->begin_frame_source();
+  } else if (!disable_display_vsync_) {
     if (gpu_vsync_control && IsGpuVSyncSignalSupported()) {
       gpu_vsync_begin_frame_source =
           base::MakeUnique<GpuVSyncBeginFrameSource>(gpu_vsync_control);
@@ -581,7 +620,6 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
                 compositor->task_runner().get()));
     begin_frame_source = synthetic_begin_frame_source.get();
   }
-  }
 
 #if defined(OS_WIN)
   gfx::RenderingWindowManager::GetInstance()->DoSetParentOnChild(
@@ -593,11 +631,16 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
   } else if (data->gpu_vsync_begin_frame_source) {
     GetFrameSinkManager()->UnregisterBeginFrameSource(
         data->gpu_vsync_begin_frame_source.get());
+  } else if (data->external_begin_frame_controller) {
+    GetFrameSinkManager()->UnregisterBeginFrameSource(
+        data->external_begin_frame_controller->begin_frame_source());
+    data->display->RemoveObserver(data->external_begin_frame_controller.get());
   }
 
   auto scheduler = base::MakeUnique<viz::DisplayScheduler>(
       begin_frame_source, compositor->task_runner().get(),
-      display_output_surface->capabilities().max_frames_pending);
+      display_output_surface->capabilities().max_frames_pending,
+      wait_for_all_pipeline_stages_before_draw_);
 
   // The Display owns and uses the |display_output_surface| created above.
   data->display = base::MakeUnique<viz::Display>(
@@ -612,6 +655,11 @@ void GpuProcessTransportFactory::EstablishedGpuChannel(
   // until we have reset |data->display|.
   data->synthetic_begin_frame_source = std::move(synthetic_begin_frame_source);
   data->gpu_vsync_begin_frame_source = std::move(gpu_vsync_begin_frame_source);
+  data->external_begin_frame_controller =
+      std::move(external_begin_frame_controller);
+
+  if (data->external_begin_frame_controller)
+    data->display->AddObserver(data->external_begin_frame_controller.get());
 
   // The |delegated_output_surface| is given back to the compositor, it
   // delegates to the Display as its root surface. Importantly, it shares the
@@ -673,6 +721,10 @@ void GpuProcessTransportFactory::RemoveCompositor(ui::Compositor* compositor) {
   } else if (data->gpu_vsync_begin_frame_source) {
     GetFrameSinkManager()->UnregisterBeginFrameSource(
         data->gpu_vsync_begin_frame_source.get());
+  } else if (data->external_begin_frame_controller) {
+    GetFrameSinkManager()->UnregisterBeginFrameSource(
+        data->external_begin_frame_controller->begin_frame_source());
+    data->display->RemoveObserver(data->external_begin_frame_controller.get());
   }
   per_compositor_data_.erase(it);
   if (per_compositor_data_.empty()) {
@@ -797,6 +849,18 @@ void GpuProcessTransportFactory::SetDisplayVSyncParameters(
   }
 }
 
+void GpuProcessTransportFactory::IssueExternalBeginFrame(
+    ui::Compositor* compositor,
+    const viz::BeginFrameArgs& args) {
+  PerCompositorDataMap::iterator it = per_compositor_data_.find(compositor);
+  if (it == per_compositor_data_.end())
+    return;
+  PerCompositorData* data = it->second.get();
+  DCHECK(data);
+  if (data->external_begin_frame_controller)
+    data->external_begin_frame_controller->IssueExternalBeginFrame(args);
+}
+
 void GpuProcessTransportFactory::SetOutputIsSecure(ui::Compositor* compositor,
                                                    bool secure) {
   PerCompositorDataMap::iterator it = per_compositor_data_.find(compositor);

content/browser/compositor/gpu_process_transport_factory.h

@@ -81,6 +81,8 @@ class GpuProcessTransportFactory : public ui::ContextFactory,
   void SetDisplayVSyncParameters(ui::Compositor* compositor,
                                  base::TimeTicks timebase,
                                  base::TimeDelta interval) override;
+  void IssueExternalBeginFrame(ui::Compositor* compositor,
+                               const viz::BeginFrameArgs& args) override;
   void SetOutputIsSecure(ui::Compositor* compositor, bool secure) override;
 
   // ImageTransportFactory implementation.
@@ -135,6 +137,7 @@ class GpuProcessTransportFactory : public ui::ContextFactory,
       shared_worker_context_provider_;
 
   bool disable_display_vsync_ = false;
+  bool wait_for_all_pipeline_stages_before_draw_ = false;
   bool shared_vulkan_context_provider_initialized_ = false;
   scoped_refptr<cc::VulkanInProcessContextProvider>
       shared_vulkan_context_provider_;

content/browser/renderer_host/render_process_host_impl.cc

@@ -2598,6 +2598,7 @@ void RenderProcessHostImpl::PropagateBrowserCommandLineToRenderer(
     cc::switches::kSlowDownRasterScaleFactor,
     cc::switches::kBrowserControlsHideThreshold,
     cc::switches::kBrowserControlsShowThreshold,
+    cc::switches::kRunAllCompositorStagesBeforeDraw,
     switches::kEnableSurfaceReferences,
     switches::kEnableSurfaceSynchronization,
 

content/renderer/gpu/render_widget_compositor.cc

@@ -551,6 +551,9 @@ cc::LayerTreeSettings RenderWidgetCompositor::GenerateLayerTreeSettings(
   settings.disallow_non_exact_resource_reuse =
       cmd.HasSwitch(cc::switches::kDisallowNonExactResourceReuse);
 
+  settings.wait_for_all_pipeline_stages_before_draw =
+      cmd.HasSwitch(cc::switches::kRunAllCompositorStagesBeforeDraw);
+
   return settings;
 }
 

ui/compositor/BUILD.gn

@@ -35,6 +35,7 @@ component("compositor") {
     "debug_utils.h",
     "dip_util.cc",
     "dip_util.h",
+    "external_begin_frame_client.h",
     "float_animation_curve_adapter.cc",
     "float_animation_curve_adapter.h",
     "layer.cc",

ui/compositor/compositor.cc

@@ -43,6 +43,7 @@
 #include "ui/compositor/compositor_switches.h"
 #include "ui/compositor/compositor_vsync_manager.h"
 #include "ui/compositor/dip_util.h"
+#include "ui/compositor/external_begin_frame_client.h"
 #include "ui/compositor/layer.h"
 #include "ui/compositor/layer_animator_collection.h"
 #include "ui/compositor/scoped_animation_duration_scale_mode.h"
@@ -58,12 +59,14 @@ Compositor::Compositor(const viz::FrameSinkId& frame_sink_id,
                        ui::ContextFactory* context_factory,
                        ui::ContextFactoryPrivate* context_factory_private,
                        scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-                       bool enable_surface_synchronization)
+                       bool enable_surface_synchronization,
+                       bool external_begin_frames_enabled)
     : context_factory_(context_factory),
       context_factory_private_(context_factory_private),
       frame_sink_id_(frame_sink_id),
       task_runner_(task_runner),
       vsync_manager_(new CompositorVSyncManager()),
+      external_begin_frames_enabled_(external_begin_frames_enabled),
       layer_animator_collection_(this),
       scheduled_timeout_(base::TimeTicks()),
       allow_locks_to_extend_timeout_(false),
@@ -165,6 +168,9 @@ Compositor::Compositor(const viz::FrameSinkId& frame_sink_id,
   settings.disallow_non_exact_resource_reuse =
       command_line->HasSwitch(cc::switches::kDisallowNonExactResourceReuse);
 
+  settings.wait_for_all_pipeline_stages_before_draw =
+      command_line->HasSwitch(cc::switches::kRunAllCompositorStagesBeforeDraw);
+
   base::TimeTicks before_create = base::TimeTicks::Now();
 
   animation_host_ = cc::AnimationHost::CreateMainInstance();
@@ -438,6 +444,34 @@ scoped_refptr<CompositorVSyncManager> Compositor::vsync_manager() const {
   return vsync_manager_;
 }
 
+void Compositor::IssueExternalBeginFrame(const viz::BeginFrameArgs& args) {
+  DCHECK(external_begin_frames_enabled_);
+  if (context_factory_private_)
+    context_factory_private_->IssueExternalBeginFrame(this, args);
+}
+
+void Compositor::SetExternalBeginFrameClient(ExternalBeginFrameClient* client) {
+  DCHECK(external_begin_frames_enabled_);
+  external_begin_frame_client_ = client;
+  if (needs_external_begin_frames_)
+    external_begin_frame_client_->OnNeedsExternalBeginFrames(true);
+}
+
+void Compositor::OnDisplayDidFinishFrame(const viz::BeginFrameAck& ack) {
+  DCHECK(external_begin_frames_enabled_);
+  if (external_begin_frame_client_)
+    external_begin_frame_client_->OnDisplayDidFinishFrame(ack);
+}
+
+void Compositor::OnNeedsExternalBeginFrames(bool needs_begin_frames) {
+  DCHECK(external_begin_frames_enabled_);
+  if (external_begin_frame_client_) {
+    external_begin_frame_client_->OnNeedsExternalBeginFrames(
+        needs_begin_frames);
+  }
+  needs_external_begin_frames_ = needs_begin_frames;
+}
+
 void Compositor::AddObserver(CompositorObserver* observer) {
   observer_list_.AddObserver(observer);
 }

ui/compositor/compositor.h

@@ -69,6 +69,7 @@ namespace ui {
 
 class Compositor;
 class CompositorVSyncManager;
+class ExternalBeginFrameClient;
 class LatencyInfo;
 class Layer;
 class Reflector;
@@ -133,6 +134,8 @@ class COMPOSITOR_EXPORT ContextFactoryPrivate {
   virtual void SetDisplayVSyncParameters(ui::Compositor* compositor,
                                          base::TimeTicks timebase,
                                          base::TimeDelta interval) = 0;
+  virtual void IssueExternalBeginFrame(ui::Compositor* compositor,
+                                       const viz::BeginFrameArgs& args) = 0;
 
   virtual void SetOutputIsSecure(Compositor* compositor, bool secure) = 0;
 };
@@ -188,7 +191,8 @@ class COMPOSITOR_EXPORT Compositor
              ui::ContextFactory* context_factory,
              ui::ContextFactoryPrivate* context_factory_private,
              scoped_refptr<base::SingleThreadTaskRunner> task_runner,
-             bool enable_surface_synchronization);
+             bool enable_surface_synchronization,
+             bool external_begin_frames_enabled = false);
   ~Compositor() override;
 
   ui::ContextFactory* context_factory() { return context_factory_; }
@@ -291,6 +295,24 @@ class COMPOSITOR_EXPORT Compositor
   // Returns the vsync manager for this compositor.
   scoped_refptr<CompositorVSyncManager> vsync_manager() const;
 
+  bool external_begin_frames_enabled() {
+    return external_begin_frames_enabled_;
+  }
+
+  void SetExternalBeginFrameClient(ExternalBeginFrameClient* client);
+
+  // The ExternalBeginFrameClient calls this to issue a BeginFrame with the
+  // given |args|.
+  void IssueExternalBeginFrame(const viz::BeginFrameArgs& args);
+
+  // Called by the ContextFactory when a BeginFrame was completed by the Display
+  // if the enable_external_begin_frames setting is true.
+  void OnDisplayDidFinishFrame(const viz::BeginFrameAck& ack);
+
+  // Called by the ContextFactory to signal whether BeginFrames are needed by
+  // the compositor if the enable_external_begin_frames setting is true.
+  void OnNeedsExternalBeginFrames(bool needs_begin_frames);
+
   // Returns the main thread task runner this compositor uses. Users of the
   // compositor generally shouldn't use this.
   scoped_refptr<base::SingleThreadTaskRunner> task_runner() const {
@@ -421,6 +443,10 @@ class COMPOSITOR_EXPORT Compositor
   // The manager of vsync parameters for this compositor.
   scoped_refptr<CompositorVSyncManager> vsync_manager_;
 
+  bool external_begin_frames_enabled_;
+  ExternalBeginFrameClient* external_begin_frame_client_ = nullptr;
+  bool needs_external_begin_frames_ = false;
+
   // The device scale factor of the monitor that this compositor is compositing
   // layers on.
   float device_scale_factor_ = 0.f;

ui/compositor/external_begin_frame_client.h

+// Copyright (c) 2017 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.
+
+#ifndef UI_COMPOSITOR_EXTERNAL_BEGIN_FRAME_CLIENT_H_
+#define UI_COMPOSITOR_EXTERNAL_BEGIN_FRAME_CLIENT_H_
+
+#include "components/viz/common/frame_sinks/begin_frame_args.h"
+#include "ui/compositor/compositor_export.h"
+
+namespace ui {
+
+class COMPOSITOR_EXPORT ExternalBeginFrameClient {
+ public:
+  virtual ~ExternalBeginFrameClient() {}
+
+  virtual void OnDisplayDidFinishFrame(const viz::BeginFrameAck& ack) = 0;
+  virtual void OnNeedsExternalBeginFrames(bool needs_begin_frames) = 0;
+};
+
+}  // namespace ui
+
+#endif  // UI_COMPOSITOR_EXTERNAL_BEGIN_FRAME_CLIENT_H_

ui/compositor/test/in_process_context_factory.h

@@ -83,6 +83,8 @@ class InProcessContextFactory : public ContextFactory,
   void SetDisplayVSyncParameters(ui::Compositor* compositor,
                                  base::TimeTicks timebase,
                                  base::TimeDelta interval) override {}
+  void IssueExternalBeginFrame(ui::Compositor* compositor,
+                               const viz::BeginFrameArgs& args) override {}
   void SetOutputIsSecure(ui::Compositor* compositor, bool secure) override {}
   const viz::ResourceSettings& GetResourceSettings() const override;
   void AddObserver(ContextFactoryObserver* observer) override;