cc: Use BeginFrameArgs

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"
 
 namespace cc {
 
 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
     : settings_(settings),
+      output_surface_state_(OUTPUT_SURFACE_LOST),
+      begin_frame_state_(BEGIN_FRAME_STATE_IDLE),
       commit_state_(COMMIT_STATE_IDLE),
+      texture_state_(LAYER_TEXTURE_STATE_UNLOCKED),
+      readback_state_(READBACK_STATE_IDLE),
+      forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
       commit_count_(0),
-      current_frame_number_(0),
-      last_frame_number_where_begin_frame_sent_to_main_thread_(-1),
-      last_frame_number_where_draw_was_called_(-1),
-      last_frame_number_where_tree_activation_attempted_(-1),
-      last_frame_number_where_update_visible_tiles_was_called_(-1),
+      begin_frame_count_(0),
+      draw_attempt_count_(0),
+      last_begin_frame_count_swap_performed_(-1),
+      last_draw_attempt_count_draw_was_called_(-1),
+      last_begin_frame_count_begin_frame_sent_to_main_thread_(-1),
+      last_draw_attempt_count_tree_activation_attempted_(-1),
+      last_draw_attempt_count_update_visible_tiles_was_called_(-1),
       consecutive_failed_draws_(0),
       maximum_number_of_failed_draws_before_draw_is_forced_(3),
       needs_redraw_(false),
       swap_used_incomplete_tile_(false),
-      needs_forced_redraw_(false),
-      needs_forced_redraw_after_next_commit_(false),
-      needs_redraw_after_next_commit_(false),
       needs_commit_(false),
-      needs_forced_commit_(false),
-      expect_immediate_begin_frame_for_main_thread_(false),
       main_thread_needs_layer_textures_(false),
-      inside_begin_frame_(false),
+      active_tree_has_been_drawn_(false),
+      active_tree_is_null_(true),
       visible_(false),
       can_start_(false),
       can_draw_(false),
       has_pending_tree_(false),
+      pending_tree_is_ready_for_activation_(false),
       draw_if_possible_failed_(false),
-      texture_state_(LAYER_TEXTURE_STATE_UNLOCKED),
-      output_surface_state_(OUTPUT_SURFACE_LOST),
       did_create_and_initialize_first_output_surface_(false) {}
 
 std::string SchedulerStateMachine::ToString() {
   std::string str;
   base::StringAppendF(&str,
                       "settings_.impl_side_painting = %d; ",
                       settings_.impl_side_painting);
+  base::StringAppendF(
+      &str, "output_surface_state_ = %d; ", output_surface_state_);
+  base::StringAppendF(&str, "begin_frame_state_ = %d; ", begin_frame_state_);
   base::StringAppendF(&str, "commit_state_ = %d; ", commit_state_);
+  base::StringAppendF(&str, "texture_state_ = %d; ", texture_state_);
+  base::StringAppendF(&str, "readback_state_ = %d; ", readback_state_);
+  base::StringAppendF(
+      &str, "forced_redraw_state_ = %d; ", forced_redraw_state_);
   base::StringAppendF(&str, "commit_count_ = %d; ", commit_count_);
-  base::StringAppendF(
-      &str, "current_frame_number_ = %d; ", current_frame_number_);
+  base::StringAppendF(&str, "begin_frame_count_ = %d; ", begin_frame_count_);
+  base::StringAppendF(&str, "draw_attempt_count_ = %d; ", draw_attempt_count_);
   base::StringAppendF(&str,
-                      "last_frame_number_where_draw_was_called_ = %d; ",
-                      last_frame_number_where_draw_was_called_);
+                      "last_begin_frame_count_swap_performed_ = %d; ",
+                      last_begin_frame_count_swap_performed_);
+  base::StringAppendF(&str,
+                      "last_draw_attempt_count_draw_was_called_ = %d; ",
+                      last_draw_attempt_count_draw_was_called_);
   base::StringAppendF(
       &str,
-      "last_frame_number_where_tree_activation_attempted_ = %d; ",
-      last_frame_number_where_tree_activation_attempted_);
+      "last_begin_frame_count_begin_frame_sent_to_main_thread_ = %d; ",
+      last_begin_frame_count_begin_frame_sent_to_main_thread_);
   base::StringAppendF(
       &str,
-      "last_frame_number_where_update_visible_tiles_was_called_ = %d; ",
-      last_frame_number_where_update_visible_tiles_was_called_);
+      "last_draw_attempt_count_tree_activation_attempted_ = %d; ",
+      last_draw_attempt_count_tree_activation_attempted_);
+  base::StringAppendF(
+      &str,
+      "last_draw_attempt_count_update_visible_tiles_was_called_ = %d; ",
+      last_draw_attempt_count_update_visible_tiles_was_called_);
   base::StringAppendF(
       &str, "consecutive_failed_draws_ = %d; ", consecutive_failed_draws_);
   base::StringAppendF(
       &str,
       "maximum_number_of_failed_draws_before_draw_is_forced_ = %d; ",
       maximum_number_of_failed_draws_before_draw_is_forced_);
   base::StringAppendF(&str, "needs_redraw_ = %d; ", needs_redraw_);
   base::StringAppendF(
       &str, "swap_used_incomplete_tile_ = %d; ", swap_used_incomplete_tile_);
-  base::StringAppendF(
-      &str, "needs_forced_redraw_ = %d; ", needs_forced_redraw_);
-  base::StringAppendF(&str,
-                      "needs_forced_redraw_after_next_commit_ = %d; ",
-                      needs_forced_redraw_after_next_commit_);
   base::StringAppendF(&str, "needs_commit_ = %d; ", needs_commit_);
-  base::StringAppendF(
-      &str, "needs_forced_commit_ = %d; ", needs_forced_commit_);
-  base::StringAppendF(&str,
-                      "expect_immediate_begin_frame_for_main_thread_ = %d; ",
-                      expect_immediate_begin_frame_for_main_thread_);
   base::StringAppendF(&str,
                       "main_thread_needs_layer_textures_ = %d; ",
                       main_thread_needs_layer_textures_);
-  base::StringAppendF(&str, "inside_begin_frame_ = %d; ",
-      inside_begin_frame_);
   base::StringAppendF(&str, "last_frame_time_ = %" PRId64 "; ",
       (last_begin_frame_args_.frame_time - base::TimeTicks())
           .InMilliseconds());
   base::StringAppendF(&str, "last_deadline_ = %" PRId64 "; ",
       (last_begin_frame_args_.deadline - base::TimeTicks()).InMilliseconds());
   base::StringAppendF(&str, "last_interval_ = %" PRId64 "; ",
       last_begin_frame_args_.interval.InMilliseconds());
   base::StringAppendF(&str, "visible_ = %d; ", visible_);
   base::StringAppendF(&str, "can_start_ = %d; ", can_start_);
   base::StringAppendF(&str, "can_draw_ = %d; ", can_draw_);
   base::StringAppendF(
       &str, "draw_if_possible_failed_ = %d; ", draw_if_possible_failed_);
   base::StringAppendF(&str, "has_pending_tree_ = %d; ", has_pending_tree_);
-  base::StringAppendF(&str, "texture_state_ = %d; ", texture_state_);
+  base::StringAppendF(&str,
+                      "pending_tree_is_ready_for_activation_ = %d; ",
+                      pending_tree_is_ready_for_activation_);
   base::StringAppendF(
-      &str, "output_surface_state_ = %d; ", output_surface_state_);
+      &str, "active_tree_has_been_drawn_ = %d; ", active_tree_has_been_drawn_);
+  base::StringAppendF(
+      &str, "active_tree_is_null_ = %d; ", active_tree_is_null_);
   return str;
 }
 
 bool SchedulerStateMachine::HasDrawnThisFrame() const {
-  return current_frame_number_ == last_frame_number_where_draw_was_called_;
+  return begin_frame_count_ == last_begin_frame_count_swap_performed_;
 }
 
-bool SchedulerStateMachine::HasAttemptedTreeActivationThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_tree_activation_attempted_;
+bool SchedulerStateMachine::HasDrawnThisDrawAttempt() const {
+  return draw_attempt_count_ == last_draw_attempt_count_draw_was_called_;
 }
 
-bool SchedulerStateMachine::HasUpdatedVisibleTilesThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_update_visible_tiles_was_called_;
+bool SchedulerStateMachine::HasSentBeginFrameToMainThreadThisFrame() const {
+  return begin_frame_count_ ==
+         last_begin_frame_count_begin_frame_sent_to_main_thread_;
 }
 
-void SchedulerStateMachine::SetPostCommitFlags() {
-  // This post-commit work is common to both completed and aborted commits.
-  if (needs_forced_redraw_after_next_commit_) {
-    needs_forced_redraw_after_next_commit_ = false;
-    needs_forced_redraw_ = true;
+bool SchedulerStateMachine::HasUpdatedVisibleTilesThisDrawAttempt() const {
+  return draw_attempt_count_ ==
+         last_draw_attempt_count_update_visible_tiles_was_called_;
+}
+
+bool SchedulerStateMachine::HasActivatedPendingTreeThisDrawAttempt() const {
+  return draw_attempt_count_ ==
+         last_draw_attempt_count_tree_activation_attempted_;
+}
+
+void SchedulerStateMachine::HandleCommitInternal(bool commit_was_aborted) {
+  commit_count_++;
+  draw_attempt_count_++;
+
+  // If we are impl-side-painting but the commit was aborted, then we behave
+  // as if we are not impl-side-painting since there is no pending tree.
+  if (settings_.impl_side_painting && !commit_was_aborted) {
+    commit_state_ = COMMIT_STATE_WAITING_FOR_ACTIVATION;
+
+    if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT)
+      output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION;
+
+    if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
+      forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION;
+    else if (readback_state_ == READBACK_STATE_FORCED_COMMIT_PENDING)
+      readback_state_ = READBACK_STATE_WAITING_FOR_ACTIVATION;
+    else if (readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_PENDING)
+      readback_state_ = READBACK_STATE_REPLACEMENT_COMMIT_ACTIVATING;
+
+  } else {
+    if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT) {
+      output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
+      needs_redraw_ = true;
+    }
+
+    if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
+      forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
+    else if (readback_state_ == READBACK_STATE_FORCED_COMMIT_PENDING)
+      readback_state_ = READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK;
+    else if (readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_PENDING)
+      readback_state_ = READBACK_STATE_IDLE;
+
+    if (draw_if_possible_failed_) {
+      last_begin_frame_count_swap_performed_ = -1;
+      last_draw_attempt_count_draw_was_called_ = -1;
+    }
+
+    if (commit_was_aborted) {
+      if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW ||
+          readback_state_ == READBACK_STATE_FORCED_COMMIT_PENDING)
+        commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
+      else
+        commit_state_ = COMMIT_STATE_IDLE;
+    } else {
+      commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
+      active_tree_has_been_drawn_ = false;
+      needs_redraw_ = true;
+    }
   }
-  if (needs_redraw_after_next_commit_) {
-    needs_redraw_after_next_commit_ = false;
-    needs_redraw_ = true;
-  }
+
   texture_state_ = LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD;
 }
 
 bool SchedulerStateMachine::DrawSuspendedUntilCommit() const {
   if (!can_draw_)
     return true;
   if (!visible_)
     return true;
   if (texture_state_ == LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD)
     return true;
   return false;
 }
 
 bool SchedulerStateMachine::ScheduledToDraw() const {
   if (!needs_redraw_)
     return false;
   if (DrawSuspendedUntilCommit())
     return false;
   return true;
 }
 
 bool SchedulerStateMachine::ShouldDraw() const {
-  if (needs_forced_redraw_)
+  if (HasDrawnThisDrawAttempt())
+    return false;
+
+  // After a readback, make sure not to draw again until we've replaced the
+  // readback commit with a real one.
+  if (readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_PENDING ||
+      readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_ACTIVATING)
+    return false;
+
+  // Draw outside of the BeginFrame deadline for readbacks.
+  if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK) {
+    DCHECK_EQ(commit_state_, COMMIT_STATE_WAITING_FOR_FIRST_DRAW);
     return true;
+  }
+
+  // If we've lost the output surface or draw is suspended, we want to be able
+  // to abort a draw and make forward progress to unblock the main thread.
+  if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+      DrawSuspendedUntilCommit()) {
+    return !active_tree_has_been_drawn_ &&
+           (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_DRAW ||
+            commit_state_ == COMMIT_STATE_WAITING_FOR_ACTIVATION ||
+            (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
+             !active_tree_is_null_));
+  }
+
+  // Except for the cases above, do not draw outside of the BeginFrame deadline.
+  if (begin_frame_state_ != BEGIN_FRAME_STATE_INSIDE_DEADLINE)
+    return false;
+
+  // Only handle forced redraws due to timeouts on the regular deadline.
+  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW) {
+    DCHECK_EQ(commit_state_, COMMIT_STATE_WAITING_FOR_FIRST_DRAW);
+    return true;
+  }
 
   if (!ScheduledToDraw())
     return false;
-  if (!inside_begin_frame_)
-    return false;
   if (HasDrawnThisFrame())
     return false;
   if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
     return false;
   return true;
 }
 
-bool SchedulerStateMachine::ShouldAttemptTreeActivation() const {
-  return has_pending_tree_ && inside_begin_frame_ &&
-         !HasAttemptedTreeActivationThisFrame();
+bool SchedulerStateMachine::ShouldActivatePendingTree() const {
+  // Some quick early outs.
+  if (!has_pending_tree_)
+    return false;
+  if (HasActivatedPendingTreeThisDrawAttempt())
+    return false;
+
+  // If this is our first activation, we don't want to activate early.
+  if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
+    return pending_tree_is_ready_for_activation_;
+
+  // In these cases, we want to activate even if the pending tree isn't ready
+  // because we aren't going to draw the pending tree or need to make
+  // forward progress to unblock the main thread.
+  if (!visible_ || output_surface_state_ == OUTPUT_SURFACE_LOST ||
+      output_surface_state_ == OUTPUT_SURFACE_CREATING ||
+      output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT)
+    return true;
+
+  // After this line, we only want to activate if we are ready to activate.
+  if (!pending_tree_is_ready_for_activation_)
+    return false;
+
+  // We do not want to activate a second tree before drawing the first one.
+  // Note: If we cannot draw, activation will eventually be unblocked by
+  // ACTION_DRAW_AND_SWAP_ABORT which will set active_tree_has_been_drawn_.
+  return active_tree_has_been_drawn_ || active_tree_is_null_;
 }
 
 bool SchedulerStateMachine::ShouldUpdateVisibleTiles() const {
   if (!settings_.impl_side_painting)
     return false;
-  if (HasUpdatedVisibleTilesThisFrame())
+  if (HasUpdatedVisibleTilesThisDrawAttempt())
     return false;
 
-  return ShouldAttemptTreeActivation() || ShouldDraw() ||
+  return ShouldActivatePendingTree() || ShouldDraw() ||
          swap_used_incomplete_tile_;
 }
 
 bool SchedulerStateMachine::ShouldAcquireLayerTexturesForMainThread() const {
   if (!main_thread_needs_layer_textures_)
     return false;
   if (texture_state_ == LAYER_TEXTURE_STATE_UNLOCKED)
     return true;
   DCHECK_EQ(texture_state_, LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD);
   // Transfer the lock from impl thread to main thread immediately if the
   // impl thread is not even scheduled to draw. Guards against deadlocking.
   if (!ScheduledToDraw())
     return true;
   if (!BeginFrameNeededToDrawByImplThread())
     return true;
   return false;
 }
 
+bool SchedulerStateMachine::ShouldSendBeginFrameToMainThread() const {
+  if (HasSentBeginFrameToMainThreadThisFrame())
+    return false;
+
+  // Only send BeginFrame to the main thread when idle.
+  if (commit_state_ != COMMIT_STATE_IDLE)
+    return false;
+
+  // We can't accept a commit if we have a pending tree.
+  if (has_pending_tree_)
+    return false;
+
+  // We want to handle readback commits ASAP.
+  if (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED)
+    return !CommitPending();
+
+  // We want to start the first commit after we get a new output surface
+  // immediately.
+  if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT &&
+      needs_commit_)
+    return true;
+
+  // We usually want to slave the main thread's BeginFrame to the impl thread's
+  // BeginFrame. However, if we aren't expecting a BeginFrame on the impl
+  // thread, we should send a BeginFrame to the main thread anyway to make
+  // progress.
+  // TODO(brianderson): Also allow sending BeginFrame to main thread while idle
+  // when the main thread isn't consuming user input.
+  if (begin_frame_state_ == BEGIN_FRAME_STATE_IDLE &&
+      BeginFrameNeededByImplThread())
+    return false;
+
+  // Do not send begin frame to main thread in the deadline until we have drawn.
+  // We have a train to catch!
+  if (begin_frame_state_ == BEGIN_FRAME_STATE_INSIDE_DEADLINE &&
+      !HasDrawnThisFrame())
+    return false;
+
+  // If not impl-side-painting, do not send a BeginFrame to the main thread if
+  // we haven't drawn the active tree. Otherwise, the commit overwrite the
+  // active tree before we have a chance to draw it.
+  if (!settings_.impl_side_painting && !active_tree_has_been_drawn_ &&
+      !active_tree_is_null_)
+    return false;
+
+  bool can_commit =
+      needs_commit_ && (visible_ || forced_redraw_state_ ==
+                                        FORCED_REDRAW_STATE_WAITING_FOR_COMMIT);
+  return can_commit &&
+         (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT ||
+          HasInitializedOutputSurface());
+}
+
 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   if (ShouldAcquireLayerTexturesForMainThread())
     return ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD;
 
   switch (commit_state_) {
-    case COMMIT_STATE_IDLE: {
-      if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
-          needs_forced_redraw_)
-        return ACTION_DRAW_FORCED;
-      if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
-          needs_forced_commit_)
-        // TODO(enne): Should probably drop the active tree on force commit.
-        return has_pending_tree_ ? ACTION_NONE
-                                 : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
+    case COMMIT_STATE_IDLE:
+      if (ShouldSendBeginFrameToMainThread())
+        return ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       if (output_surface_state_ == OUTPUT_SURFACE_LOST && can_start_)
         return ACTION_BEGIN_OUTPUT_SURFACE_CREATION;
       if (output_surface_state_ == OUTPUT_SURFACE_CREATING)
         return ACTION_NONE;
       if (ShouldUpdateVisibleTiles())
         return ACTION_UPDATE_VISIBLE_TILES;
-      if (ShouldAttemptTreeActivation())
-        return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
+      if (ShouldActivatePendingTree())
+        return ACTION_ACTIVATE_PENDING_TREE;
       if (ShouldDraw()) {
-        return needs_forced_redraw_ ? ACTION_DRAW_FORCED
-                                    : ACTION_DRAW_IF_POSSIBLE;
+        if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+            DrawSuspendedUntilCommit())
+          return ACTION_DRAW_AND_SWAP_ABORT;
+        else
+          return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
       }
-      bool can_commit_this_frame =
-          visible_ &&
-          current_frame_number_ >
-              last_frame_number_where_begin_frame_sent_to_main_thread_;
-      if (needs_commit_ && ((can_commit_this_frame &&
-                             output_surface_state_ == OUTPUT_SURFACE_ACTIVE) ||
-                            needs_forced_commit_))
-        // TODO(enne): Should probably drop the active tree on force commit.
-        return has_pending_tree_ ? ACTION_NONE
-                                 : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       return ACTION_NONE;
-    }
+
     case COMMIT_STATE_FRAME_IN_PROGRESS:
       if (ShouldUpdateVisibleTiles())
         return ACTION_UPDATE_VISIBLE_TILES;
-      if (ShouldAttemptTreeActivation())
-        return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
+      if (ShouldActivatePendingTree())
+        return ACTION_ACTIVATE_PENDING_TREE;
       if (ShouldDraw()) {
-        return needs_forced_redraw_ ? ACTION_DRAW_FORCED
-                                    : ACTION_DRAW_IF_POSSIBLE;
+        if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+            DrawSuspendedUntilCommit())
+          return ACTION_DRAW_AND_SWAP_ABORT;
+        else
+          return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
       }
       return ACTION_NONE;
 
     case COMMIT_STATE_READY_TO_COMMIT:
       return ACTION_COMMIT;
 
+    case COMMIT_STATE_WAITING_FOR_ACTIVATION: {
+      if (ShouldUpdateVisibleTiles())
+        return ACTION_UPDATE_VISIBLE_TILES;
+      if (ShouldActivatePendingTree())
+        return ACTION_ACTIVATE_PENDING_TREE;
+      if (ShouldDraw()) {
+        if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+            DrawSuspendedUntilCommit())
+          return ACTION_DRAW_AND_SWAP_ABORT;
+        else
+          return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
+      }
+      return ACTION_NONE;
+    }
+
     case COMMIT_STATE_WAITING_FOR_FIRST_DRAW: {
       if (ShouldUpdateVisibleTiles())
         return ACTION_UPDATE_VISIBLE_TILES;
-      if (ShouldAttemptTreeActivation())
-        return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
-      if (ShouldDraw() || output_surface_state_ == OUTPUT_SURFACE_LOST) {
-        return needs_forced_redraw_ ? ACTION_DRAW_FORCED
-                                    : ACTION_DRAW_IF_POSSIBLE;
+      if (ShouldActivatePendingTree())
+        return ACTION_ACTIVATE_PENDING_TREE;
+      if (ShouldDraw()) {
+        if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
+          return ACTION_DRAW_AND_SWAP_FORCED;
+        else if (readback_state_ ==
+                 READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK)
+          return ACTION_DRAW_AND_READBACK;
+        else if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+                 DrawSuspendedUntilCommit())
+          return ACTION_DRAW_AND_SWAP_ABORT;
+        else
+          return ACTION_DRAW_AND_SWAP_IF_POSSIBLE;
       }
-      // COMMIT_STATE_WAITING_FOR_FIRST_DRAW wants to enforce a draw. If
-      // can_draw_ is false or textures are not available, proceed to the next
-      // step (similar as in COMMIT_STATE_IDLE).
-      bool can_commit =
-          needs_forced_commit_ ||
-          (visible_ &&
-           current_frame_number_ >
-               last_frame_number_where_begin_frame_sent_to_main_thread_);
-      if (needs_commit_ && can_commit && DrawSuspendedUntilCommit())
-        return has_pending_tree_ ? ACTION_NONE
-                                 : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       return ACTION_NONE;
     }
-
-    case COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW:
-      if (ShouldUpdateVisibleTiles())
-        return ACTION_UPDATE_VISIBLE_TILES;
-      if (ShouldAttemptTreeActivation())
-        return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
-      if (needs_forced_redraw_)
-        return ACTION_DRAW_FORCED;
-      return ACTION_NONE;
   }
   NOTREACHED();
   return ACTION_NONE;
 }
 
 void SchedulerStateMachine::UpdateState(Action action) {
   switch (action) {
     case ACTION_NONE:
       return;
 
     case ACTION_UPDATE_VISIBLE_TILES:
-      last_frame_number_where_update_visible_tiles_was_called_ =
-          current_frame_number_;
+      last_draw_attempt_count_update_visible_tiles_was_called_ =
+          draw_attempt_count_;
       return;
 
-    case ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED:
-      last_frame_number_where_tree_activation_attempted_ =
-          current_frame_number_;
+    case ACTION_ACTIVATE_PENDING_TREE:
+      last_draw_attempt_count_tree_activation_attempted_ = draw_attempt_count_;
       return;
 
     case ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD:
       DCHECK(!has_pending_tree_);
-      if (!needs_forced_commit_) {
-        DCHECK(visible_);
-        DCHECK_GT(current_frame_number_,
-                  last_frame_number_where_begin_frame_sent_to_main_thread_);
-      }
+      DCHECK(visible_ ||
+             readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED ||
+             forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT ||
+             output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT);
       commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
       needs_commit_ = false;
-      needs_forced_commit_ = false;
-      last_frame_number_where_begin_frame_sent_to_main_thread_ =
-          current_frame_number_;
+      if (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED)
+        readback_state_ = READBACK_STATE_FORCED_COMMIT_PENDING;
+      last_begin_frame_count_begin_frame_sent_to_main_thread_ =
+          begin_frame_count_;
       return;
 
     case ACTION_COMMIT:
-      commit_count_++;
-      if (expect_immediate_begin_frame_for_main_thread_)
-        commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
-      else
-        commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
-      // When impl-side painting, we draw on activation instead of on commit.
-      if (!settings_.impl_side_painting)
-        needs_redraw_ = true;
-      if (draw_if_possible_failed_)
-        last_frame_number_where_draw_was_called_ = -1;
-      SetPostCommitFlags();
+      HandleCommitInternal(false);
       return;
 
-    case ACTION_DRAW_FORCED:
-    case ACTION_DRAW_IF_POSSIBLE:
-      needs_redraw_ = false;
-      needs_forced_redraw_ = false;
-      draw_if_possible_failed_ = false;
-      swap_used_incomplete_tile_ = false;
-      if (inside_begin_frame_)
-        last_frame_number_where_draw_was_called_ = current_frame_number_;
-      if (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW) {
-        DCHECK(expect_immediate_begin_frame_for_main_thread_);
-        commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
-        expect_immediate_begin_frame_for_main_thread_ = false;
-      } else if (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_DRAW) {
-        commit_state_ = COMMIT_STATE_IDLE;
-      }
-      if (texture_state_ == LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD)
-        texture_state_ = LAYER_TEXTURE_STATE_UNLOCKED;
+    case ACTION_DRAW_AND_SWAP_IF_POSSIBLE:
+    case ACTION_DRAW_AND_SWAP_FORCED:
+      UpdateStateOnDraw(true);
+      return;
+
+    case ACTION_DRAW_AND_READBACK:
+    case ACTION_DRAW_AND_SWAP_ABORT:
+      UpdateStateOnDraw(false);
       return;
 
     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
       DCHECK_EQ(commit_state_, COMMIT_STATE_IDLE);
       DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_LOST);
       output_surface_state_ = OUTPUT_SURFACE_CREATING;
       return;
 
     case ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD:
       texture_state_ = LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD;
       main_thread_needs_layer_textures_ = false;
       return;
   }
 }
 
+void SchedulerStateMachine::UpdateStateOnDraw(bool did_swap) {
+  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW) {
+    commit_state_ = COMMIT_STATE_IDLE;
+    forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
+  } else if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK) {
+    DCHECK(!has_pending_tree_);
+    commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
+    readback_state_ = READBACK_STATE_REPLACEMENT_COMMIT_PENDING;
+  } else if (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_DRAW) {
+    commit_state_ = COMMIT_STATE_IDLE;
+  }
+
+  if (texture_state_ == LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD)
+    texture_state_ = LAYER_TEXTURE_STATE_UNLOCKED;
+
+  needs_redraw_ = false;
+  active_tree_has_been_drawn_ = true;
+  draw_if_possible_failed_ = false;
+  last_draw_attempt_count_draw_was_called_ = draw_attempt_count_;
+
+  if (did_swap) {
+    swap_used_incomplete_tile_ = false;
+    last_begin_frame_count_swap_performed_ = begin_frame_count_;
+  }
+}
+
+void SchedulerStateMachine::AdvanceBeginFrameStateWhenNoActionsRemain() {
+  switch (begin_frame_state_) {
+    case BEGIN_FRAME_STATE_INSIDE_BEGIN_FRAME:
+      begin_frame_state_ = BEGIN_FRAME_STATE_DEADLINE_PENDING;
+      break;
+    case BEGIN_FRAME_STATE_INSIDE_DEADLINE:
+      begin_frame_state_ = BEGIN_FRAME_STATE_IDLE;
+      break;
+    case BEGIN_FRAME_STATE_IDLE:
+    case BEGIN_FRAME_STATE_DEADLINE_PENDING:
+      break;
+  }
+}
+
 void SchedulerStateMachine::SetMainThreadNeedsLayerTextures() {
   DCHECK(!main_thread_needs_layer_textures_);
   DCHECK_NE(texture_state_, LAYER_TEXTURE_STATE_ACQUIRED_BY_MAIN_THREAD);
   main_thread_needs_layer_textures_ = true;
 }
 
+bool SchedulerStateMachine::BeginFrameNeededByImplThread() const {
+  return BeginFrameNeededToDrawByImplThread() ||
+         BeginFrameProactivelyNeededByImplThread();
+}
+
 bool SchedulerStateMachine::BeginFrameNeededToDrawByImplThread() const {
   // If we can't draw, don't tick until we are notified that we can draw again.
   if (!can_draw_)
     return false;
 
-  if (needs_forced_redraw_)
+  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
     return true;
 
   if (visible_ && swap_used_incomplete_tile_)
     return true;
 
-  return needs_redraw_ && visible_ &&
-         output_surface_state_ == OUTPUT_SURFACE_ACTIVE;
+  return needs_redraw_ && visible_ && HasInitializedOutputSurface();
 }
 
-bool SchedulerStateMachine::ProactiveBeginFrameWantedByImplThread() const {
-  // Do not be proactive when invisible.
-  if (!visible_ || output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
+bool SchedulerStateMachine::BeginFrameProactivelyNeededByImplThread() const {
+  if (settings_.using_synchronous_renderer_compositor)
+    return false;
+
+  if (!settings_.throttle_frame_production)
+    return false;
+
+  if (!visible_ || !HasInitializedOutputSurface())
     return false;
 
   // We should proactively request a BeginFrame if a commit or a tree activation
   // is pending.
-  return (needs_commit_ || needs_forced_commit_ ||
-          commit_state_ != COMMIT_STATE_IDLE || has_pending_tree_);
+  return (needs_commit_ || commit_state_ != COMMIT_STATE_IDLE ||
+          has_pending_tree_);
 }
 
-void SchedulerStateMachine::DidEnterBeginFrame(const BeginFrameArgs& args) {
-  current_frame_number_++;
-  inside_begin_frame_ = true;
+void SchedulerStateMachine::OnBeginFrame(const BeginFrameArgs& args) {
+  begin_frame_count_++;
+  draw_attempt_count_++;
   last_begin_frame_args_ = args;
+  begin_frame_state_ = BEGIN_FRAME_STATE_INSIDE_BEGIN_FRAME;
 }
 
-void SchedulerStateMachine::DidLeaveBeginFrame() {
-  inside_begin_frame_ = false;
+bool SchedulerStateMachine::ShouldTriggerBeginFrameDeadlineEarly() const {
+  // TODO(brianderson): This should take into account multiple commit sources.
+  return begin_frame_state_ == BEGIN_FRAME_STATE_DEADLINE_PENDING &&
+         !active_tree_has_been_drawn_;
+}
+
+bool SchedulerStateMachine::InsideBeginFrame() const {
+  return begin_frame_state_ != BEGIN_FRAME_STATE_IDLE;
+}
+
+void SchedulerStateMachine::OnBeginFrameDeadline() {
+  DCHECK_EQ(begin_frame_state_, BEGIN_FRAME_STATE_DEADLINE_PENDING);
+  draw_attempt_count_++;
+  begin_frame_state_ = BEGIN_FRAME_STATE_INSIDE_DEADLINE;
 }
 
 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 
 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 
 void SchedulerStateMachine::DidSwapUseIncompleteTile() {
   swap_used_incomplete_tile_ = true;
 }
 
-void SchedulerStateMachine::SetNeedsForcedRedraw() {
-  needs_forced_redraw_ = true;
-}
-
 void SchedulerStateMachine::DidDrawIfPossibleCompleted(bool success) {
   draw_if_possible_failed_ = !success;
   if (draw_if_possible_failed_) {
     needs_redraw_ = true;
     needs_commit_ = true;
     consecutive_failed_draws_++;
     if (settings_.timeout_and_draw_when_animation_checkerboards &&
         consecutive_failed_draws_ >=
         maximum_number_of_failed_draws_before_draw_is_forced_) {
       consecutive_failed_draws_ = 0;
       // We need to force a draw, but it doesn't make sense to do this until
       // we've committed and have new textures.
-      needs_forced_redraw_after_next_commit_ = true;
+      forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_COMMIT;
     }
   } else {
     consecutive_failed_draws_ = 0;
   }
 }
 
 void SchedulerStateMachine::SetNeedsCommit() { needs_commit_ = true; }
 
-void SchedulerStateMachine::SetNeedsForcedCommit() {
-  needs_forced_commit_ = true;
-  expect_immediate_begin_frame_for_main_thread_ = true;
+void SchedulerStateMachine::SetNeedsForcedCommitForReadback() {
+  DCHECK(readback_state_ == READBACK_STATE_IDLE ||
+         readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_PENDING);
+  if (commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS)
+    readback_state_ = READBACK_STATE_FORCED_COMMIT_PENDING;
+  else
+    readback_state_ = READBACK_STATE_FORCED_COMMIT_REQUESTED;
 }
 
 void SchedulerStateMachine::FinishCommit() {
   DCHECK(commit_state_ == COMMIT_STATE_FRAME_IN_PROGRESS ||
-         (expect_immediate_begin_frame_for_main_thread_ &&
-          commit_state_ != COMMIT_STATE_IDLE))
+         readback_state_ == READBACK_STATE_FORCED_COMMIT_PENDING)
       << ToString();
   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
 }
 
 void SchedulerStateMachine::BeginFrameAbortedByMainThread(bool did_handle) {
   DCHECK_EQ(commit_state_, COMMIT_STATE_FRAME_IN_PROGRESS);
-  if (expect_immediate_begin_frame_for_main_thread_) {
-    expect_immediate_begin_frame_for_main_thread_ = false;
+  if (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED) {
+    readback_state_ = READBACK_STATE_IDLE;
   } else if (did_handle) {
-    commit_state_ = COMMIT_STATE_IDLE;
-    SetPostCommitFlags();
+    HandleCommitInternal(true);
   } else {
     commit_state_ = COMMIT_STATE_IDLE;
     SetNeedsCommit();
   }
 }
 
 void SchedulerStateMachine::DidLoseOutputSurface() {
   if (output_surface_state_ == OUTPUT_SURFACE_LOST ||
       output_surface_state_ == OUTPUT_SURFACE_CREATING)
     return;
   output_surface_state_ = OUTPUT_SURFACE_LOST;
+  needs_redraw_ = false;
 }
 
-void SchedulerStateMachine::SetHasPendingTree(bool has_pending_tree) {
+void SchedulerStateMachine::NotifyReadyToActivate() {
+  if (has_pending_tree_)
+    pending_tree_is_ready_for_activation_ = true;
+}
+
+void SchedulerStateMachine::SetHasTrees(bool has_pending_tree,
+                                        bool active_tree_is_null) {
+  active_tree_is_null_ = active_tree_is_null;
+  if (has_pending_tree_ && !has_pending_tree) {
+    // There is a new active tree.
+    draw_attempt_count_++;
+    pending_tree_is_ready_for_activation_ = false;
+    active_tree_has_been_drawn_ = false;
+    needs_redraw_ = true;
+
+    if (draw_if_possible_failed_) {
+      last_begin_frame_count_swap_performed_ = -1;
+      last_draw_attempt_count_draw_was_called_ = -1;
+    }
+
+    if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
+      output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
+
+    DCHECK_EQ(COMMIT_STATE_WAITING_FOR_ACTIVATION, commit_state_);
+    if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION) {
+      commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
+      forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
+    } else if (readback_state_ == READBACK_STATE_WAITING_FOR_ACTIVATION) {
+      commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_DRAW;
+      readback_state_ = READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK;
+    } else {
+      commit_state_ = COMMIT_STATE_IDLE;
+      if (readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_ACTIVATING)
+        readback_state_ = READBACK_STATE_IDLE;
+    }
+  } else if (!has_pending_tree_ && has_pending_tree) {
+    // There is a new pending tree.
+    pending_tree_is_ready_for_activation_ = false;
+  }
+
   has_pending_tree_ = has_pending_tree;
 }
 
-void SchedulerStateMachine::SetCanDraw(bool can) { can_draw_ = can; }
+void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
 
 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
-  output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
-
-  if (did_create_and_initialize_first_output_surface_) {
-    // TODO(boliu): See if we can remove this when impl-side painting is always
-    // on. Does anything on the main thread need to update after recreate?
+  output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
+  if (did_create_and_initialize_first_output_surface_)
     needs_commit_ = true;
-    // If anything has requested a redraw, we don't want to actually draw
-    // when the output surface is restored until things have a chance to
-    // sort themselves out with a commit.
-    needs_redraw_ = false;
-  }
-  needs_redraw_after_next_commit_ = true;
   did_create_and_initialize_first_output_surface_ = true;
 }
 
 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
-  return output_surface_state_ == OUTPUT_SURFACE_ACTIVE;
+  return output_surface_state_ != OUTPUT_SURFACE_LOST &&
+         output_surface_state_ != OUTPUT_SURFACE_CREATING;
 }
 
 void SchedulerStateMachine::SetMaximumNumberOfFailedDrawsBeforeDrawIsForced(
     int num_draws) {
   maximum_number_of_failed_draws_before_draw_is_forced_ = num_draws;
 }
 
 }  // namespace cc