cc: Properly detect when child Surfaces idle

cc/surfaces/display_scheduler.cc

 // Copyright 2015 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/surfaces/display_scheduler.h"
 
 #include <vector>
 
 #include "base/stl_util.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 88 matching lines @@
 
 void DisplayScheduler::DrawAndSwap() {
   TRACE_EVENT0("cc", "DisplayScheduler::DrawAndSwap");
   DCHECK_LT(pending_swaps_, max_pending_swaps_);
   DCHECK(!output_surface_lost_);
 
   bool success = client_->DrawAndSwap();
   if (!success)
     return;
 
-  needs_draw_ = false;
-  entire_display_damaged_ = false;
-  all_active_child_surfaces_ready_to_draw_ = false;
-
-  expect_damage_from_root_surface_ = root_surface_damaged_;
-  root_surface_damaged_ = false;
-
   child_surface_ids_to_expect_damage_from_ =
       base::STLSetIntersection<std::vector<SurfaceId>>(
           child_surface_ids_damaged_, child_surface_ids_damaged_prev_);
 
   child_surface_ids_damaged_prev_.swap(child_surface_ids_damaged_);
   child_surface_ids_damaged_.clear();
+
+  needs_draw_ = false;
+  entire_display_damaged_ = false;
+  all_active_child_surfaces_ready_to_draw_ =
+      child_surface_ids_to_expect_damage_from_.empty();
+
+  expect_damage_from_root_surface_ = root_surface_damaged_;
+  root_surface_damaged_ = false;
 }
 
 bool DisplayScheduler::OnBeginFrameMixInDelegate(const BeginFrameArgs& args) {
   base::TimeTicks now = base::TimeTicks::Now();
   TRACE_EVENT2("cc", "DisplayScheduler::BeginFrame", "args", args.AsValue(),
                "now", now);
 
   // Only service missed BeginFrames if they haven't already expired.
   base::TimeTicks adjusted_deadline =
       args.deadline - BeginFrameArgs::DefaultEstimatedParentDrawTime();
@@ skipping 118 matching lines @@
 
 void DisplayScheduler::AttemptDrawAndSwap() {
   inside_begin_frame_deadline_interval_ = false;
   begin_frame_deadline_task_.Cancel();
   begin_frame_deadline_task_time_ = base::TimeTicks();
 
   if (needs_draw_ && !output_surface_lost_) {
     if (pending_swaps_ < max_pending_swaps_ && !root_surface_resources_locked_)
       DrawAndSwap();
   } else {
+    // We are going idle, so reset expectations.
+    child_surface_ids_to_expect_damage_from_.clear();
+    child_surface_ids_damaged_prev_.clear();
+    child_surface_ids_damaged_.clear();
+    all_active_child_surfaces_ready_to_draw_ = true;
+    expect_damage_from_root_surface_ = false;
+
     begin_frame_source_->SetNeedsBeginFrames(false);
   }
 }
 
 void DisplayScheduler::OnBeginFrameDeadline() {
   TRACE_EVENT0("cc", "DisplayScheduler::OnBeginFrameDeadline");
 
   AttemptDrawAndSwap();
   begin_frame_source_->DidFinishFrame(0);
 }
 
 void DisplayScheduler::DidSwapBuffers() {
   pending_swaps_++;
   TRACE_EVENT1("cc", "DisplayScheduler::DidSwapBuffers", "pending_frames",
                pending_swaps_);
 }
 
 void DisplayScheduler::DidSwapBuffersComplete() {
   pending_swaps_--;
   TRACE_EVENT1("cc", "DisplayScheduler::DidSwapBuffersComplete",
                "pending_frames", pending_swaps_);
   ScheduleBeginFrameDeadline();
 }
 
 }  // namespace cc