[cc] Calculate the correct latest_confirmed_sequence_number in cc::Scheduler.

cc/scheduler/scheduler.cc

 // Copyright 2011 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 "cc/scheduler/scheduler.h"
 
 #include <algorithm>
 
 #include "base/auto_reset.h"
 #include "base/logging.h"
@@ skipping 304 matching lines @@
   BeginFrameArgs adjusted_args = args;
   // Cancel the missed begin frame task in case the BFS sends a begin frame
   // before the missed frame task runs.
   missed_begin_frame_task_.Cancel();
 
   base::TimeTicks now = Now();
 
   // Discard missed begin frames if they are too late.
   if (adjusted_args.type == BeginFrameArgs::MISSED &&
       now > adjusted_args.deadline) {
-    // TODO(eseckler): Determine and set correct |ack.latest_confirmed_frame|.
-    BeginFrameAck ack(adjusted_args.source_id, adjusted_args.sequence_number,
-                      adjusted_args.sequence_number, 0, false);
+    BeginFrameAck ack(
+        adjusted_args.source_id, adjusted_args.sequence_number,
+        state_machine_.last_frame_number_compositor_frame_was_fresh(), 0,
+        false);
     begin_frame_source_->DidFinishFrame(this, ack);
     return;
   }
 
   // Run the previous deadline if any.
   if (state_machine_.begin_impl_frame_state() ==
       SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_INSIDE_BEGIN_FRAME) {
     OnBeginImplFrameDeadline();
     // We may not need begin frames any longer.
     if (!observing_begin_frame_source_) {
-      // TODO(eseckler): Determine and set correct |ack.latest_confirmed_frame|.
-      BeginFrameAck ack(adjusted_args.source_id, adjusted_args.sequence_number,
-                        adjusted_args.sequence_number, 0, false);
+      BeginFrameAck ack(
+          adjusted_args.source_id, adjusted_args.sequence_number,
+          state_machine_.last_frame_number_compositor_frame_was_fresh(), 0,
+          false);
       begin_frame_source_->DidFinishFrame(this, ack);
       return;
     }
   }
   DCHECK_EQ(state_machine_.begin_impl_frame_state(),
             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
 
   bool main_thread_is_in_high_latency_mode =
       state_machine_.main_thread_missed_last_deadline();
   TRACE_EVENT2("cc,benchmark", "Scheduler::BeginImplFrame", "args",
@@ skipping 40 matching lines @@
 
   if (ShouldRecoverMainLatency(adjusted_args, can_activate_before_deadline)) {
     TRACE_EVENT_INSTANT0("cc", "SkipBeginMainFrameToReduceLatency",
                          TRACE_EVENT_SCOPE_THREAD);
     state_machine_.SetSkipNextBeginMainFrameToReduceLatency();
   } else if (ShouldRecoverImplLatency(adjusted_args,
                                       can_activate_before_deadline)) {
     TRACE_EVENT_INSTANT0("cc", "SkipBeginImplFrameToReduceLatency",
                          TRACE_EVENT_SCOPE_THREAD);
     if (begin_frame_source_) {
-      // TODO(eseckler): Determine and set correct |ack.latest_confirmed_frame|.
-      BeginFrameAck ack(adjusted_args.source_id, adjusted_args.sequence_number,
-                        adjusted_args.sequence_number, 0, false);
+      BeginFrameAck ack(
+          adjusted_args.source_id, adjusted_args.sequence_number,
+          state_machine_.last_frame_number_compositor_frame_was_fresh(), 0,
+          false);
       begin_frame_source_->DidFinishFrame(this, ack);
     }
     return;
   }
 
   BeginImplFrame(adjusted_args);
 }
 
 void Scheduler::BeginImplFrameSynchronous(const BeginFrameArgs& args) {
   TRACE_EVENT1("cc,benchmark", "Scheduler::BeginImplFrame", "args",
@@ skipping 10 matching lines @@
       state_machine_.needs_redraw());
   FinishImplFrame();
 }
 
 void Scheduler::FinishImplFrame() {
   state_machine_.OnBeginImplFrameIdle();
   ProcessScheduledActions();
 
   client_->DidFinishImplFrame();
   if (begin_frame_source_) {
-    // TODO(eseckler): Determine and set correct |ack.latest_confirmed_frame|.
-    BeginFrameAck ack(begin_main_frame_args_.source_id,
-                      begin_main_frame_args_.sequence_number,
-                      begin_main_frame_args_.sequence_number, 0,
-                      state_machine_.did_submit_in_last_frame());
+    BeginFrameAck ack(
+        begin_main_frame_args_.source_id,

[brianderson, 2017/01/13 19:13:49]

The begin_main_frame_args_.source_id at this point might not correspond to the
same source_id that created last_frame_number_compositor_frame_was_fresh. I
think you'll need to track multiple source_ids through the pipeline just like
you did with the last_frame_number*s.

[Sami, 2017/01/16 10:41:02]

I think this is okay, because when the source_id changes we reset everything to
be fresh up to that point, which is effectively doing the same thing as would
checking source_id here. However Eric noticed we're not always telling the state
machine when the source_id might change, so he's gonna fix that still. FWIW we
also decided to reset to everything to kInvalidSequenceNumber to make it more
obvious that there was a discontinuity.

[Eric Seckler, 2017/01/16 14:33:01]

What Sami said. :) Regarding telling the state machine about source_id changes,
I'm now telling it about every BeginFrame received by the Scheduler to update
the sequence numbers even in cases where we skip a BeginImplFrame().

[Eric Seckler, 2017/01/17 18:01:24]

Badum.. I'm just realizing that this is broken since
BeginImplFrameWithDeadline() may trigger the previous BeginFrame's deadline.
I'll have to think about a different solution for this... :)

+        begin_main_frame_args_.sequence_number,
+        state_machine_.last_frame_number_compositor_frame_was_fresh(), 0,
+        state_machine_.did_submit_in_last_frame());
     begin_frame_source_->DidFinishFrame(this, ack);
   }
   begin_impl_frame_tracker_.Finish();
 }
 
 // BeginImplFrame starts a compositor frame that will wait up until a deadline
 // for a BeginMainFrame+activation to complete before it times out and draws
 // any asynchronous animation and scroll/pinch updates.
 void Scheduler::BeginImplFrame(const BeginFrameArgs& args) {
   DCHECK_EQ(state_machine_.begin_impl_frame_state(),
             SchedulerStateMachine::BEGIN_IMPL_FRAME_STATE_IDLE);
   DCHECK(begin_impl_frame_deadline_task_.IsCancelled());
   DCHECK(state_machine_.HasInitializedCompositorFrameSink());
 
   begin_impl_frame_tracker_.Start(args);
-  state_machine_.OnBeginImplFrame();
+  state_machine_.OnBeginImplFrame(args.source_id, args.sequence_number);
   devtools_instrumentation::DidBeginFrame(layer_tree_host_id_);
   compositor_timing_history_->WillBeginImplFrame(
       state_machine_.NewActiveTreeLikely());
   client_->WillBeginImplFrame(begin_impl_frame_tracker_.Current());
 
   ProcessScheduledActions();
 }
 
 void Scheduler::ScheduleBeginImplFrameDeadline() {
   // The synchronous compositor does not post a deadline task.
@@ skipping 302 matching lines @@
 }
 
 bool Scheduler::IsBeginMainFrameSentOrStarted() const {
   return (state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_SENT ||
           state_machine_.begin_main_frame_state() ==
               SchedulerStateMachine::BEGIN_MAIN_FRAME_STATE_STARTED);
 }
 
 }  // namespace cc