Don't defer commit until draw if not drawing soon

cc/scheduler/scheduler_state_machine.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_state_machine.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 445 matching lines @@
 bool SchedulerStateMachine::ShouldCommit() const {
   if (commit_state_ != COMMIT_STATE_READY_TO_COMMIT)
     return false;
 
   // We must not finish the commit until the pending tree is free.
   if (has_pending_tree_) {
     DCHECK(settings_.main_frame_before_activation_enabled);
     return false;
   }
 
-  // Prioritize drawing the previous commit before finishing the next commit.
-  if (active_tree_needs_first_draw_)
-    return false;
+  if (settings_.impl_side_painting) {
+    // Prioritize drawing the previous commit before finishing the next commit.
+    bool active_tree_first_draw_is_imminent =
+        active_tree_needs_first_draw_ &&
+        begin_impl_frame_state_ != BEGIN_IMPL_FRAME_STATE_IDLE &&
+        pending_swaps_ < max_pending_swaps_;
+    if (active_tree_first_draw_is_imminent)
+      return false;
+  } else {
+    // If we only have an active tree, it is incorrect to replace it
+    // before we've drawn it.
+    if (active_tree_needs_first_draw_)
+      return false;
+  }
 
   return true;
 }
 
 bool SchedulerStateMachine::ShouldPrepareTiles() const {
   // PrepareTiles only really needs to be called immediately after commit
   // and then periodically after that. Use a funnel to make sure we average
   // one PrepareTiles per BeginImplFrame in the long run.
   if (prepare_tiles_funnel_ > 0)
     return false;
@@ skipping 655 matching lines @@
       static_cast<int>(begin_impl_frame_state_),
       static_cast<int>(commit_state_),
       has_pending_tree_ ? 'T' : 'F',
       pending_tree_is_ready_for_activation_ ? 'T' : 'F',
       active_tree_needs_first_draw_ ? 'T' : 'F',
       max_pending_swaps_,
       pending_swaps_);
 }
 
 }  // namespace cc