Retry tree activation if raster tasks finish during first half of vsync interval

cc/trees/thread_proxy.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/trees/thread_proxy.h"
 
 #include "base/auto_reset.h"
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "cc/base/thread.h"
@@ skipping 10 matching lines @@
 #include "cc/trees/layer_tree_impl.h"
 
 namespace {
 
 // Measured in seconds.
 const double kContextRecreationTickRate = 0.03;
 
 // Measured in seconds.
 const double kSmoothnessTakesPriorityExpirationDelay = 0.25;
 
+// Time period in seconds from the previous vsync during which we are allowed to
+// retry tree activation and rendering.
+const double kTreeActivationGracePeriod = 0.008;
+
 }  // namespace
 
 namespace cc {
 
 scoped_ptr<Proxy> ThreadProxy::Create(LayerTreeHost* layer_tree_host,
                                       scoped_ptr<Thread> impl_thread) {
   return make_scoped_ptr(
       new ThreadProxy(layer_tree_host, impl_thread.Pass())).PassAs<Proxy>();
 }
 
@@ skipping 801 matching lines @@
                "ThreadProxy::ScheduledActionCheckForCompletedTileUploads");
   layer_tree_host_impl_->CheckForCompletedTileUploads();
 }
 
 void ThreadProxy::ScheduledActionActivatePendingTreeIfNeeded() {
   DCHECK(IsImplThread());
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionActivatePendingTreeIfNeeded");
   layer_tree_host_impl_->ActivatePendingTreeIfNeeded();
 }
 
+void ThreadProxy::DidFinishTileRasterTasks() {
+  DCHECK(IsImplThread());
+  TRACE_EVENT0("cc", "LayerTreeHostImpl::DidFinishTileRasterTasks");
+  base::TimeDelta time_since_vsync =
+      base::TimeTicks::Now() - scheduler_on_impl_thread_->LastVSyncTime();
+  base::TimeDelta grace_period =
+      base::TimeDelta::FromMilliseconds(kTreeActivationGracePeriod);
+  if (time_since_vsync > grace_period) {
+    TRACE_EVENT0("cc", "LayerTreeHostImpl::DidFinishTileRasterTasks: too late");
+    return;
+  }
+  if (layer_tree_host_impl_->ActivatePendingTreeIfNeeded())
+    scheduler_on_impl_thread_->VSyncTick(false);
+}
+
 void ThreadProxy::ScheduledActionBeginContextRecreation() {
   DCHECK(IsImplThread());
   Proxy::MainThread()->PostTask(
       base::Bind(&ThreadProxy::BeginContextRecreation, main_thread_weak_ptr_));
 }
 
 ScheduledActionDrawAndSwapResult
 ThreadProxy::ScheduledActionDrawAndSwapInternal(bool forced_draw) {
   TRACE_EVENT0("cc", "ThreadProxy::ScheduledActionDrawAndSwap");
 
@@ skipping 478 matching lines @@
       base::Bind(&ThreadProxy::StartScrollbarAnimationOnImplThread,
                  impl_thread_weak_ptr_),
       delay);
 }
 
 void ThreadProxy::StartScrollbarAnimationOnImplThread() {
   layer_tree_host_impl_->StartScrollbarAnimation(base::TimeTicks::Now());
 }
 
 }  // namespace cc