Refactoring the way begin frame sources inside scheduler work.

cc/scheduler/scheduler.cc

Index: cc/scheduler/scheduler.cc
diff --git a/cc/scheduler/scheduler.cc b/cc/scheduler/scheduler.cc
index e924d33884bf6dec6a758b4d640b8fef0fee8059..f39df56c693906236ff0ed70ef953d2bf8f39f77 100644
--- a/cc/scheduler/scheduler.cc
+++ b/cc/scheduler/scheduler.cc
@@ -11,76 +11,21 @@
 #include "cc/debug/devtools_instrumentation.h"
 #include "cc/debug/traced_value.h"
 #include "cc/scheduler/delay_based_time_source.h"
+#include "cc/scheduler/frame_source.h"
 #include "ui/gfx/frame_time.h"
 
 namespace cc {
 
-class SyntheticBeginFrameSource : public TimeSourceClient {
- public:
-  SyntheticBeginFrameSource(Scheduler* scheduler,
-                            base::SingleThreadTaskRunner* task_runner)
-      : scheduler_(scheduler) {
-    if (gfx::FrameTime::TimestampsAreHighRes()) {
-      time_source_ = DelayBasedTimeSourceHighRes::Create(
-          scheduler_->VSyncInterval(), task_runner);
-    } else {
-      time_source_ = DelayBasedTimeSource::Create(scheduler_->VSyncInterval(),
-                                                  task_runner);
-    }
-    time_source_->SetClient(this);
-  }
-
-  virtual ~SyntheticBeginFrameSource() {}
-
-  // Updates the phase and frequency of the timer.
-  void CommitVSyncParameters(base::TimeTicks timebase,
-                             base::TimeDelta interval) {
-    time_source_->SetTimebaseAndInterval(timebase, interval);
-  }
-
-  // Activates future BeginFrames and, if activating, pushes the most
-  // recently missed BeginFrame to the back of a retroactive queue.
-  void SetNeedsBeginFrame(bool needs_begin_frame,
-                          std::deque<BeginFrameArgs>* begin_retro_frame_args) {
-    base::TimeTicks missed_tick_time =
-        time_source_->SetActive(needs_begin_frame);
-    if (!missed_tick_time.is_null()) {
-      begin_retro_frame_args->push_back(
-          CreateSyntheticBeginFrameArgs(missed_tick_time));
-    }
-  }
-
-  // TimeSourceClient implementation of OnTimerTick triggers a BeginFrame.
-  virtual void OnTimerTick() OVERRIDE {
-    BeginFrameArgs begin_frame_args(
-        CreateSyntheticBeginFrameArgs(time_source_->LastTickTime()));
-    scheduler_->BeginFrame(begin_frame_args);
-  }
-
- private:
-  BeginFrameArgs CreateSyntheticBeginFrameArgs(base::TimeTicks frame_time) {
-    base::TimeTicks deadline =
-        time_source_->NextTickTime() - scheduler_->EstimatedParentDrawTime();
-    return BeginFrameArgs::Create(
-        frame_time, deadline, scheduler_->VSyncInterval());
-  }
-
-  Scheduler* scheduler_;
-  scoped_refptr<TimeSource> time_source_;
-};
-
 Scheduler::Scheduler(
     SchedulerClient* client,
     const SchedulerSettings& scheduler_settings,
     int layer_tree_host_id,
+    BeginFrameSource* external_frame_source,
     const scoped_refptr<base::SingleThreadTaskRunner>& impl_task_runner)
     : settings_(scheduler_settings),
       client_(client),
       layer_tree_host_id_(layer_tree_host_id),
       impl_task_runner_(impl_task_runner),
-      vsync_interval_(BeginFrameArgs::DefaultInterval()),
-      last_set_needs_begin_frame_(false),
-      begin_unthrottled_frame_posted_(false),
       begin_retro_frame_posted_(false),
       state_machine_(scheduler_settings),
       inside_process_scheduled_actions_(false),
@@ -98,8 +43,6 @@ Scheduler::Scheduler(
 
   begin_retro_frame_closure_ =
       base::Bind(&Scheduler::BeginRetroFrame, weak_factory_.GetWeakPtr());
-  begin_unthrottled_frame_closure_ =
-      base::Bind(&Scheduler::BeginUnthrottledFrame, weak_factory_.GetWeakPtr());
   begin_impl_frame_deadline_closure_ = base::Bind(
       &Scheduler::OnBeginImplFrameDeadline, weak_factory_.GetWeakPtr());
   poll_for_draw_triggers_closure_ = base::Bind(
@@ -107,32 +50,37 @@ Scheduler::Scheduler(
   advance_commit_state_closure_ = base::Bind(
       &Scheduler::PollToAdvanceCommitState, weak_factory_.GetWeakPtr());
 
-  if (!settings_.begin_frame_scheduling_enabled) {
-    SetupSyntheticBeginFrames();
-  }
-}
+  scoped_ptr<BeginFrameSource> primary_frame_source;
 
-Scheduler::~Scheduler() {
-  if (synthetic_begin_frame_source_) {
-    synthetic_begin_frame_source_->SetNeedsBeginFrame(false,
-                                                      &begin_retro_frame_args_);
+  if (!settings_.throttle_frame_production) {
+    TRACE_EVENT0("cc", "Scheduler::Scheduler() BackToBackBeginFrameSource");
+    primary_frame_source = scoped_ptr<BeginFrameSource>(
+        new BackToBackBeginFrameSource(this, impl_task_runner_));
+  } else if (settings_.begin_frame_scheduling_enabled) {
+    TRACE_EVENT0("cc", "Scheduler::Scheduler() ProxyBeginFrameSource");
+    primary_frame_source = scoped_ptr<BeginFrameSource>(
+        new ProxyBeginFrameSource(this, external_frame_source));
+  } else {
+    TRACE_EVENT0("cc", "Scheduler::Scheduler() SyntheticBeginFrameSource");
+    primary_frame_source =
+        scoped_ptr<BeginFrameSource>(new SyntheticBeginFrameSource(
+            this, impl_task_runner_, BeginFrameArgs::DefaultInterval()));
   }
+  scoped_ptr<BeginFrameSource> background_frame_source(
+      new SyntheticBeginFrameSource(
+          this, impl_task_runner_, base::TimeDelta::FromSeconds(1)));
+
+  frame_source_ = scoped_ptr<DualBeginFrameSource>(new DualBeginFrameSource(
+      this, primary_frame_source.Pass(), background_frame_source.Pass()));
 }
 
-void Scheduler::SetupSyntheticBeginFrames() {
-  DCHECK(!synthetic_begin_frame_source_);
-  synthetic_begin_frame_source_.reset(
-      new SyntheticBeginFrameSource(this, impl_task_runner_.get()));
+Scheduler::~Scheduler() {
+  frame_source_->SetGenerateFrames(false);
 }
 
 void Scheduler::CommitVSyncParameters(base::TimeTicks timebase,
                                       base::TimeDelta interval) {
-  // TODO(brianderson): We should not be receiving 0 intervals.
-  if (interval == base::TimeDelta())
-    interval = BeginFrameArgs::DefaultInterval();
-  vsync_interval_ = interval;
-  if (!settings_.begin_frame_scheduling_enabled)
-    synthetic_begin_frame_source_->CommitVSyncParameters(timebase, interval);
+  frame_source_->SetTimeBaseAndInterval(timebase, interval);
 }
 
 void Scheduler::SetEstimatedParentDrawTime(base::TimeDelta draw_time) {
@@ -146,6 +94,11 @@ void Scheduler::SetCanStart() {
 
 void Scheduler::SetVisible(bool visible) {
   state_machine_.SetVisible(visible);
+  if (visible) {
+    frame_source_->SwitchSource(frame_source_->SourceForeground());
+  } else {
+    frame_source_->SwitchSource(frame_source_->SourceBackground());
+  }
   ProcessScheduledActions();
 }
 
@@ -228,14 +181,14 @@ void Scheduler::DidManageTiles() {
 void Scheduler::DidLoseOutputSurface() {
   TRACE_EVENT0("cc", "Scheduler::DidLoseOutputSurface");
   state_machine_.DidLoseOutputSurface();
-  last_set_needs_begin_frame_ = false;
+  frame_source_->SetGenerateFrames(false);
   begin_retro_frame_args_.clear();
   ProcessScheduledActions();
 }
 
 void Scheduler::DidCreateAndInitializeOutputSurface() {
   TRACE_EVENT0("cc", "Scheduler::DidCreateAndInitializeOutputSurface");
-  DCHECK(!last_set_needs_begin_frame_);
+  DCHECK(!frame_source_->IsGeneratingFrames());
   DCHECK(begin_impl_frame_deadline_task_.IsCancelled());
   state_machine_.DidCreateAndInitializeOutputSurface();
   ProcessScheduledActions();
@@ -247,7 +200,7 @@ void Scheduler::NotifyBeginMainFrameStarted() {
 }
 
 base::TimeTicks Scheduler::AnticipatedDrawTime() const {
-  if (!last_set_needs_begin_frame_ ||
+  if (!frame_source_->IsGeneratingFrames() ||
       begin_impl_frame_args_.interval <= base::TimeDelta())
     return base::TimeTicks();
 
@@ -265,75 +218,28 @@ base::TimeTicks Scheduler::LastBeginImplFrameTime() {
 void Scheduler::SetupNextBeginFrameIfNeeded() {
   bool needs_begin_frame = state_machine_.BeginFrameNeeded();
 
-  if (settings_.throttle_frame_production) {
-    SetupNextBeginFrameWhenVSyncThrottlingEnabled(needs_begin_frame);
-  } else {
-    SetupNextBeginFrameWhenVSyncThrottlingDisabled(needs_begin_frame);
-  }
-  SetupPollingMechanisms(needs_begin_frame);
-}
-
-// When we are throttling frame production, we request BeginFrames
-// from the OutputSurface.
-void Scheduler::SetupNextBeginFrameWhenVSyncThrottlingEnabled(
-    bool needs_begin_frame) {
   bool at_end_of_deadline =
-      state_machine_.begin_impl_frame_state() ==
-          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE;
+      (state_machine_.begin_impl_frame_state() ==
+       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE) ||
+      (state_machine_.begin_impl_frame_state() ==
+       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
 
   bool should_call_set_needs_begin_frame =
       // Always request the BeginFrame immediately if it wasn't needed before.
-      (needs_begin_frame && !last_set_needs_begin_frame_) ||
+      needs_begin_frame ||
       // Only stop requesting BeginFrames after a deadline.
-      (!needs_begin_frame && last_set_needs_begin_frame_ && at_end_of_deadline);
+      (!needs_begin_frame && at_end_of_deadline);
 
   if (should_call_set_needs_begin_frame) {
-    if (settings_.begin_frame_scheduling_enabled) {
-      client_->SetNeedsBeginFrame(needs_begin_frame);
-    } else {
-      synthetic_begin_frame_source_->SetNeedsBeginFrame(
-          needs_begin_frame, &begin_retro_frame_args_);
-    }
-    last_set_needs_begin_frame_ = needs_begin_frame;
+    frame_source_->SetGenerateFrames(needs_begin_frame);
   }
 
-  PostBeginRetroFrameIfNeeded();
-}
-
-// When we aren't throttling frame production, we initiate a BeginFrame
-// as soon as one is needed.
-void Scheduler::SetupNextBeginFrameWhenVSyncThrottlingDisabled(
-    bool needs_begin_frame) {
-  last_set_needs_begin_frame_ = needs_begin_frame;
-
-  if (!needs_begin_frame || begin_unthrottled_frame_posted_)
-    return;
+  // TODO(mithro): Use pending frames properly.
+  if (at_end_of_deadline)
+    frame_source_->PendingFrames(0);
 
-  if (state_machine_.begin_impl_frame_state() !=
-          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE &&
-      state_machine_.begin_impl_frame_state() !=
-          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_DEADLINE) {
-    return;
-  }
-
-  begin_unthrottled_frame_posted_ = true;
-  impl_task_runner_->PostTask(FROM_HERE, begin_unthrottled_frame_closure_);
-}
-
-// BeginUnthrottledFrame is used when we aren't throttling frame production.
-// This will usually be because VSync is disabled.
-void Scheduler::BeginUnthrottledFrame() {
-  DCHECK(!settings_.throttle_frame_production);
-  DCHECK(begin_retro_frame_args_.empty());
-
-  base::TimeTicks now = gfx::FrameTime::Now();
-  base::TimeTicks deadline = now + vsync_interval_;
-
-  BeginFrameArgs begin_frame_args =
-      BeginFrameArgs::Create(now, deadline, vsync_interval_);
-  BeginImplFrame(begin_frame_args);
-
-  begin_unthrottled_frame_posted_ = false;
+  PostBeginRetroFrameIfNeeded();
+  SetupPollingMechanisms(needs_begin_frame);
 }
 
 // We may need to poll when we can't rely on BeginFrame to advance certain
@@ -391,7 +297,9 @@ void Scheduler::SetupPollingMechanisms(bool needs_begin_frame) {
 // a BeginRetroFrame.
 void Scheduler::BeginFrame(const BeginFrameArgs& args) {
   TRACE_EVENT1("cc", "Scheduler::BeginFrame", "args", ToTrace(args));
-  DCHECK(settings_.throttle_frame_production);
+
+  BeginFrameArgs adjusted_args(args);
+  adjusted_args.deadline -= EstimatedParentDrawTime();
 
   bool should_defer_begin_frame;
   if (settings_.using_synchronous_renderer_compositor) {
@@ -399,19 +307,22 @@ void Scheduler::BeginFrame(const BeginFrameArgs& args) {
   } else {
     should_defer_begin_frame =
         !begin_retro_frame_args_.empty() || begin_retro_frame_posted_ ||
-        !last_set_needs_begin_frame_ ||
+        !frame_source_->IsGeneratingFrames() ||
         (state_machine_.begin_impl_frame_state() !=
          SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   }
 
   if (should_defer_begin_frame) {
-    begin_retro_frame_args_.push_back(args);
-    TRACE_EVENT_INSTANT0(
-        "cc", "Scheduler::BeginFrame deferred", TRACE_EVENT_SCOPE_THREAD);
+    begin_retro_frame_args_.push_back(adjusted_args);
+    TRACE_EVENT_INSTANT1("cc",
+                         "Scheduler::BeginFrame deferred",
+                         TRACE_EVENT_SCOPE_THREAD,
+                         "args",
+                         ToTrace(adjusted_args));
     return;
   }
 
-  BeginImplFrame(args);
+  BeginImplFrame(adjusted_args);
 }
 
 // BeginRetroFrame is called for BeginFrames that we've deferred because
@@ -442,12 +353,11 @@ void Scheduler::BeginRetroFrame() {
     TRACE_EVENT1("cc",
                  "Scheduler::BeginRetroFrame discarding",
                  "frame_time",
-                 begin_retro_frame_args_.front().frame_time);
+                 ToTrace(begin_retro_frame_args_.front()));
     begin_retro_frame_args_.pop_front();
   }
 
   if (begin_retro_frame_args_.empty()) {
-    DCHECK(settings_.throttle_frame_production);
     TRACE_EVENT_INSTANT0("cc",
                          "Scheduler::BeginRetroFrames all expired",
                          TRACE_EVENT_SCOPE_THREAD);
@@ -462,7 +372,7 @@ void Scheduler::BeginRetroFrame() {
 // will check if there is a pending BeginRetroFrame to ensure we handle
 // BeginFrames in FIFO order.
 void Scheduler::PostBeginRetroFrameIfNeeded() {
-  if (!last_set_needs_begin_frame_)
+  if (!frame_source_->IsGeneratingFrames())
     return;
 
   if (begin_retro_frame_args_.empty() || begin_retro_frame_posted_)
@@ -671,19 +581,17 @@ bool Scheduler::WillDrawIfNeeded() const {
 scoped_ptr<base::Value> Scheduler::AsValue() const {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue);
   state->Set("state_machine", state_machine_.AsValue().release());
+  state->Set("frame_source",
+             frame_source_->BeginFrameSourceAsValue().release());
 
   scoped_ptr<base::DictionaryValue> scheduler_state(new base::DictionaryValue);
   scheduler_state->SetDouble(
       "time_until_anticipated_draw_time_ms",
       (AnticipatedDrawTime() - base::TimeTicks::Now()).InMillisecondsF());
-  scheduler_state->SetDouble("vsync_interval_ms",
-                             vsync_interval_.InMillisecondsF());
   scheduler_state->SetDouble("estimated_parent_draw_time_ms",
                              estimated_parent_draw_time_.InMillisecondsF());
   scheduler_state->SetBoolean("last_set_needs_begin_frame_",
-                              last_set_needs_begin_frame_);
-  scheduler_state->SetBoolean("begin_unthrottled_frame_posted_",
-                              begin_unthrottled_frame_posted_);
+                              frame_source_->IsGeneratingFrames());
   scheduler_state->SetBoolean("begin_retro_frame_posted_",
                               begin_retro_frame_posted_);
   scheduler_state->SetInteger("begin_retro_frame_args_",