cc: Use BeginFrameArgs

cc/scheduler/scheduler_state_machine.cc

Index: cc/scheduler/scheduler_state_machine.cc
diff --git a/cc/scheduler/scheduler_state_machine.cc b/cc/scheduler/scheduler_state_machine.cc
index 0b6383af5490d11804cbca162dff256b27af503a..95cb5bc0296467a5849900fe4d37c72fe6a8fbd5 100644
--- a/cc/scheduler/scheduler_state_machine.cc
+++ b/cc/scheduler/scheduler_state_machine.cc
@@ -8,27 +8,39 @@
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 
+
+class DEVNULL {};
+template <typename A>
+DEVNULL& operator <<(DEVNULL &d, A a) { return d; }
+//static DEVNULL gDevNull;
+//#undef VLOG
+//#define VLOG(x) gDevNull
+
 namespace cc {
 
 SchedulerStateMachine::SchedulerStateMachine(const SchedulerSettings& settings)
     : settings_(settings),
       commit_state_(COMMIT_STATE_IDLE),
       commit_count_(0),
-      current_frame_number_(0),
-      last_frame_number_where_draw_was_called_(-1),
-      last_frame_number_where_tree_activation_attempted_(-1),
-      last_frame_number_where_check_for_completed_tile_uploads_called_(-1),
+      begin_frame_count_(0),
+      begin_frame_deadline_count_(0),
+      draw_attempt_count_(0),
+      last_begin_frame_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_completed_tile_uploads_checked_(-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),
+      readback_state_(READBACK_STATE_IDLE),
+      forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
       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),
+      begin_frame_state_(BEGIN_FRAME_STATE_IDLE),
+      commit_tree_has_been_drawn_(true),
+      active_tree_has_been_drawn_(false),
+      active_tree_is_null_(true),
       visible_(false),
       can_start_(false),
       can_draw_(false),
@@ -45,19 +57,21 @@ std::string SchedulerStateMachine::ToString() {
                       settings_.impl_side_painting);
   base::StringAppendF(&str, "commit_state_ = %d; ", commit_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_draw_was_called_ = %d; ",
+                      last_begin_frame_count_draw_was_called_);
   base::StringAppendF(
       &str,
-      "last_frame_number_where_tree_activation_attempted_ = %d; ",
-      last_frame_number_where_tree_activation_attempted_);
+      "last_draw_attempt_count_tree_activation_attempted_ = %d; ",
+      last_draw_attempt_count_tree_activation_attempted_);
   base::StringAppendF(
       &str,
-      "last_frame_number_where_check_for_completed_tile_uploads_called_ = %d; ",
-      last_frame_number_where_check_for_completed_tile_uploads_called_);
+      "last_draw_attempt_count_completed_tile_uploads_checked_ = %d; ",
+      last_draw_attempt_count_completed_tile_uploads_checked_);
   base::StringAppendF(
       &str, "consecutive_failed_draws_ = %d; ", consecutive_failed_draws_);
   base::StringAppendF(
@@ -67,22 +81,15 @@ std::string SchedulerStateMachine::ToString() {
   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, "readback_state_ = %d; ", readback_state_);
   base::StringAppendF(&str,
-                      "needs_forced_redraw_after_next_commit_ = %d; ",
-                      needs_forced_redraw_after_next_commit_);
+                      "forced_redraw_state_ = %d; ",
+                      forced_redraw_state_);
   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, "begin_frame_state_ = %d; ", begin_frame_state_);
   base::StringAppendF(&str, "last_frame_time_ = %"PRId64"; ",
       (last_begin_frame_args_.frame_time - base::TimeTicks())
           .InMilliseconds());
@@ -96,6 +103,12 @@ std::string SchedulerStateMachine::ToString() {
   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, "commit_tree_has_been_drawn_ = %d; ",
+      commit_tree_has_been_drawn_);
+  base::StringAppendF(&str, "active_tree_has_been_drawn_ = %d; ",
+      active_tree_has_been_drawn_);
+  base::StringAppendF(&str, "active_tree_is_null_ = %d; ",
+      active_tree_is_null_);
   base::StringAppendF(&str, "texture_state_ = %d; ", texture_state_);
   base::StringAppendF(
       &str, "output_surface_state_ = %d; ", output_surface_state_);
@@ -103,17 +116,23 @@ std::string SchedulerStateMachine::ToString() {
 }
 
 bool SchedulerStateMachine::HasDrawnThisFrame() const {
-  return current_frame_number_ == last_frame_number_where_draw_was_called_;
+  return begin_frame_count_ == last_begin_frame_count_draw_was_called_;
 }
 
-bool SchedulerStateMachine::HasAttemptedTreeActivationThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_tree_activation_attempted_;
+bool SchedulerStateMachine::HasSentBeginFrameToMainThreadThisFrame() const {
+  return begin_frame_count_ ==
+         last_begin_frame_count_begin_frame_sent_to_main_thread_;
 }
 
-bool SchedulerStateMachine::HasCheckedForCompletedTileUploadsThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_check_for_completed_tile_uploads_called_;
+bool SchedulerStateMachine::HasAttemptedTreeActivationThisDrawAttempt() const {
+  return draw_attempt_count_ ==
+         last_draw_attempt_count_tree_activation_attempted_;
+}
+
+bool SchedulerStateMachine::
+    HasCheckedForCompletedTileUploadsThisDrawAttempt() const {
+  return draw_attempt_count_ ==
+         last_draw_attempt_count_completed_tile_uploads_checked_;
 }
 
 bool SchedulerStateMachine::DrawSuspendedUntilCommit() const {
@@ -135,12 +154,28 @@ bool SchedulerStateMachine::ScheduledToDraw() const {
 }
 
 bool SchedulerStateMachine::ShouldDraw() const {
-  if (needs_forced_redraw_)
-    return true;
+  // 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;
 
-  if (!ScheduledToDraw())
+  // Only draw outside of the BeginFrame deadline for readbacks or if we've
+  // lost the outpust surface or are waiting for a forced draw.
+  if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK)
+    return commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
+  if (output_surface_state_ == OUTPUT_SURFACE_LOST)
+    return commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_DRAW ||
+           commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
+
+  // Never draw outside of the BeginFrame deadline (except for readbacks).
+  if (begin_frame_state_ != BEGIN_FRAME_STATE_INSIDE_DEADLINE)
     return false;
-  if (!inside_begin_frame_)
+  if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
+    return commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
+  if (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW)
+    return false;
+  if (!ScheduledToDraw())
     return false;
   if (HasDrawnThisFrame())
     return false;
@@ -150,14 +185,18 @@ bool SchedulerStateMachine::ShouldDraw() const {
 }
 
 bool SchedulerStateMachine::ShouldAttemptTreeActivation() const {
-  return has_pending_tree_ && inside_begin_frame_ &&
-         !HasAttemptedTreeActivationThisFrame();
+  return !HasAttemptedTreeActivationThisDrawAttempt() &&
+         has_pending_tree_ &&
+         (!can_draw_ || !visible_ ||
+          output_surface_state_ != OUTPUT_SURFACE_ACTIVE ||
+          ((active_tree_has_been_drawn_ || active_tree_is_null_) &&
+           begin_frame_state_ != BEGIN_FRAME_STATE_IDLE));
 }
 
 bool SchedulerStateMachine::ShouldCheckForCompletedTileUploads() const {
   if (!settings_.impl_side_painting)
     return false;
-  if (HasCheckedForCompletedTileUploadsThisFrame())
+  if (HasCheckedForCompletedTileUploadsThisDrawAttempt())
     return false;
 
   return ShouldAttemptTreeActivation() || ShouldDraw() ||
@@ -179,17 +218,60 @@ bool SchedulerStateMachine::ShouldAcquireLayerTexturesForMainThread() const {
   return false;
 }
 
+bool SchedulerStateMachine::ShouldSendBeginFrameToMainThread() const {
+  if (HasSentBeginFrameToMainThreadThisFrame())
+    return false;
+
+  if (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED)
+    return true;
+
+  // TODO(brianderson): 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.
+  if (begin_frame_state_ == BEGIN_FRAME_STATE_INSIDE_DEADLINE &&
+      !HasDrawnThisFrame())
+    return false;
+
+  // We can't accept a commit if we have a pending tree.
+  if (has_pending_tree_)
+    return false;
+
+  bool can_commit = needs_commit_ &&
+      (visible_ ||
+       forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT);
+  switch (commit_state_) {
+    case COMMIT_STATE_IDLE:
+      return can_commit &&
+          (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT ||
+           output_surface_state_ == OUTPUT_SURFACE_ACTIVE);
+
+    // COMMIT_STATE_WAITING_FOR_ACTIVATION wants to enforce activation and
+    // eventually a draw.
+    // 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).
+    case COMMIT_STATE_WAITING_FOR_ACTIVATION:
+    case COMMIT_STATE_WAITING_FOR_FIRST_DRAW:
+      return can_commit && DrawSuspendedUntilCommit();
+    default:
+      return false;
+  }
+
+  return false;
+}
+
 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;
+    case COMMIT_STATE_IDLE: VLOG(0) << __LINE__ << "COMMIT_STATE_IDLE\n";
       if (output_surface_state_ != OUTPUT_SURFACE_ACTIVE &&
-          needs_forced_commit_)
+          readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED)
         // TODO(enne): Should probably drop the active tree on force commit.
         return has_pending_tree_ ? ACTION_NONE
                                  : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
@@ -202,57 +284,73 @@ SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
       if (ShouldDraw()) {
-        return needs_forced_redraw_ ? ACTION_DRAW_FORCED
-                                    : ACTION_DRAW_IF_POSSIBLE;
+        DCHECK_NE(forced_redraw_state_, FORCED_REDRAW_STATE_WAITING_FOR_DRAW);
+        DCHECK_NE(readback_state_, READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK);
+        return ACTION_DRAW_IF_POSSIBLE;
       }
-      if (needs_commit_ &&
-          ((visible_ && output_surface_state_ == OUTPUT_SURFACE_ACTIVE)
-           || needs_forced_commit_))
+      if (ShouldSendBeginFrameToMainThread()) {
         // 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_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
+      }
       return ACTION_NONE;
 
-    case COMMIT_STATE_FRAME_IN_PROGRESS:
+    case COMMIT_STATE_FRAME_IN_PROGRESS:VLOG(0) << __LINE__ << "COMMIT_STATE_FRAME_IN_PROGRESS\n";
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
       if (ShouldDraw()) {
-        return needs_forced_redraw_ ? ACTION_DRAW_FORCED
-                                    : ACTION_DRAW_IF_POSSIBLE;
+        DCHECK_NE(forced_redraw_state_, FORCED_REDRAW_STATE_WAITING_FOR_DRAW);
+        DCHECK_NE(readback_state_, READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK);
+        return ACTION_DRAW_IF_POSSIBLE;
       }
       return ACTION_NONE;
 
-    case COMMIT_STATE_READY_TO_COMMIT:
+    case COMMIT_STATE_READY_TO_COMMIT:VLOG(0) << __LINE__ << "COMMIT_STATE_READY_TO_COMMIT\n";
       return ACTION_COMMIT;
 
-    case COMMIT_STATE_WAITING_FOR_FIRST_DRAW: {
+    case COMMIT_STATE_WAITING_FOR_ACTIVATION: { VLOG(0) << __LINE__ << "COMMIT_STATE_WAITING_FOR_ACTIVATION\n";
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       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 (ShouldDraw()) {
+        DCHECK_NE(forced_redraw_state_, FORCED_REDRAW_STATE_WAITING_FOR_DRAW);
+        DCHECK_NE(readback_state_, READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK);
+        return ACTION_DRAW_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 = visible_ || needs_forced_commit_;
-      if (needs_commit_ && can_commit && DrawSuspendedUntilCommit())
-        return has_pending_tree_ ? ACTION_NONE
-                                 : ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
+      if (ShouldSendBeginFrameToMainThread())
+        return ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
       return ACTION_NONE;
     }
 
-    case COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW:
+    case COMMIT_STATE_WAITING_FOR_FIRST_DRAW: { VLOG(0) << __LINE__ << "COMMIT_STATE_WAITING_FOR_FIRST_DRAW\n";
       if (ShouldCheckForCompletedTileUploads())
         return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
       if (ShouldAttemptTreeActivation())
         return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
-      if (needs_forced_redraw_)
-        return ACTION_DRAW_FORCED;
+      if (ShouldDraw()) {
+        DCHECK_NE(forced_redraw_state_, FORCED_REDRAW_STATE_WAITING_FOR_DRAW);
+        DCHECK_NE(readback_state_, READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK);
+        return ACTION_DRAW_IF_POSSIBLE;
+      }
+      if (ShouldSendBeginFrameToMainThread())
+        return ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD;
+      return ACTION_NONE;
+    }
+
+    case COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW: VLOG(0) << __LINE__ << "COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW\n";
+      if (ShouldCheckForCompletedTileUploads())
+        return ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS;
+      if (ShouldAttemptTreeActivation())
+        return ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED;
+      if (ShouldDraw()) {
+        if(forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
+          return ACTION_DRAW_FORCED;
+        else if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK)
+          return ACTION_DRAW_AND_READBACK;
+        NOTREACHED();
+      }
       return ACTION_NONE;
   }
   NOTREACHED();
@@ -265,60 +363,88 @@ void SchedulerStateMachine::UpdateState(Action action) {
       return;
 
     case ACTION_CHECK_FOR_COMPLETED_TILE_UPLOADS:
-      last_frame_number_where_check_for_completed_tile_uploads_called_ =
-          current_frame_number_;
+      last_draw_attempt_count_completed_tile_uploads_checked_ =
+          draw_attempt_count_;
       return;
 
     case ACTION_ACTIVATE_PENDING_TREE_IF_NEEDED:
-      last_frame_number_where_tree_activation_attempted_ =
-          current_frame_number_;
+      last_draw_attempt_count_tree_activation_attempted_ =
+          draw_attempt_count_;
       return;
 
     case ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD:
       DCHECK(!has_pending_tree_);
-      DCHECK(visible_ || needs_forced_commit_);
+      DCHECK(visible_ ||
+             readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED ||
+             forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) << ToString();
       commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
       needs_commit_ = false;
-      needs_forced_commit_ = false;
+      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;
 
-      if (needs_forced_redraw_after_next_commit_) {
-        needs_forced_redraw_after_next_commit_ = false;
-        needs_forced_redraw_ = true;
+      if (settings_.impl_side_painting) {
+        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;
+        commit_state_ = COMMIT_STATE_WAITING_FOR_ACTIVATION;
+      } else {
+        if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT) {
+          forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
+          commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
+        } else if (readback_state_ == READBACK_STATE_FORCED_COMMIT_PENDING ||
+                   readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED) {
+          readback_state_ = READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK;
+          commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_FORCED_DRAW;
+        } else {
+          if (readback_state_ == READBACK_STATE_REPLACEMENT_COMMIT_PENDING)
+            readback_state_ = READBACK_STATE_IDLE;
+          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_begin_frame_count_draw_was_called_ = -1;
+      }
+      commit_tree_has_been_drawn_ = false;
       texture_state_ = LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD;
       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_;
+    case ACTION_DRAW_FORCED:
+    case ACTION_DRAW_AND_READBACK:
       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;
+        if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW) {
+          forced_redraw_state_ = FORCED_REDRAW_STATE_IDLE;
+        } else if (readback_state_ ==
+                   READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK) {
+          commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
+          readback_state_ = has_pending_tree_ ?
+              READBACK_STATE_REPLACEMENT_COMMIT_ACTIVATING :
+              READBACK_STATE_REPLACEMENT_COMMIT_PENDING;
+        }
       } else if (commit_state_ == COMMIT_STATE_WAITING_FOR_FIRST_DRAW) {
         commit_state_ = COMMIT_STATE_IDLE;
       }
+      needs_redraw_ = false;
+      draw_if_possible_failed_ = false;
+      swap_used_incomplete_tile_ = false;
+      last_begin_frame_count_draw_was_called_ = begin_frame_count_;
       if (texture_state_ == LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD)
         texture_state_ = LAYER_TEXTURE_STATE_UNLOCKED;
+      active_tree_has_been_drawn_ = true;
+      commit_tree_has_been_drawn_ = true;
       return;
 
     case ACTION_BEGIN_OUTPUT_SURFACE_CREATION:
@@ -336,18 +462,37 @@ void SchedulerStateMachine::UpdateState(Action action) {
   }
 }
 
+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_)
@@ -357,28 +502,57 @@ bool SchedulerStateMachine::BeginFrameNeededToDrawByImplThread() const {
          output_surface_state_ == OUTPUT_SURFACE_ACTIVE;
 }
 
-bool SchedulerStateMachine::ProactiveBeginFrameWantedByImplThread() const {
-  // Do not be proactive when invisible.
+bool SchedulerStateMachine::BeginFrameProactivelyNeededByImplThread() const {
+  if (settings_.using_synchronous_renderer_compositor)
+    return false;
+
+  if (!settings_.throttle_frame_production)
+    return false;
+
   if (!visible_ || output_surface_state_ != OUTPUT_SURFACE_ACTIVE)
     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) {
-  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;
+}
+
+bool SchedulerStateMachine::ShouldTriggerBeginFrameDeadlineEarly() const {
+  // TODO(brianderson): This should take into account multiple commit sources.
+  return begin_frame_state_ == BEGIN_FRAME_STATE_DEADLINE_PENDING &&
+         WillDrawNewTree();
+}
+
+bool SchedulerStateMachine::InsideBeginFrame() const {
+  return begin_frame_state_ != BEGIN_FRAME_STATE_IDLE;
+}
+
+bool SchedulerStateMachine::WillDrawNewTree() const {
+  if (settings_.impl_side_painting)
+    return !active_tree_has_been_drawn_;
+  else
+    return !commit_tree_has_been_drawn_;
 }
 
-void SchedulerStateMachine::DidLeaveBeginFrame() {
-  current_frame_number_++;
-  inside_begin_frame_ = false;
+void SchedulerStateMachine::OnBeginFrameDeadline() {
+  DCHECK_EQ(begin_frame_state_, BEGIN_FRAME_STATE_DEADLINE_PENDING);
+  begin_frame_deadline_count_++;
+  draw_attempt_count_++;
+  begin_frame_state_ = BEGIN_FRAME_STATE_INSIDE_DEADLINE;
 }
 
-void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
+void SchedulerStateMachine::SetVisible(bool visible) {
+  visible_ = visible;
+}
 
 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 
@@ -386,10 +560,6 @@ 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_) {
@@ -402,7 +572,7 @@ void SchedulerStateMachine::DidDrawIfPossibleCompleted(bool success) {
       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;
@@ -411,23 +581,24 @@ void SchedulerStateMachine::DidDrawIfPossibleCompleted(bool success) {
 
 void SchedulerStateMachine::SetNeedsCommit() { needs_commit_ = true; }
 
-void SchedulerStateMachine::SetNeedsForcedCommit() {
-  needs_forced_commit_ = true;
-  expect_immediate_begin_frame_for_main_thread_ = true;
+void SchedulerStateMachine::SetNeedsForcedCommitForReadback() {
+  VLOG(0) << __LINE__ << "SetNeedsForcedCommitForReadback\n";
+  DCHECK_EQ(readback_state_, READBACK_STATE_IDLE);
+  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_ &&
+         (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED &&
           commit_state_ != COMMIT_STATE_IDLE))
       << ToString();
   commit_state_ = COMMIT_STATE_READY_TO_COMMIT;
 }
 
 void SchedulerStateMachine::BeginFrameAbortedByMainThread() {
-  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;
+  DCHECK_EQ(commit_state_, COMMIT_STATE_FRAME_IN_PROGRESS) << ToString();
+  if (readback_state_ == READBACK_STATE_FORCED_COMMIT_REQUESTED) {
+    readback_state_ = READBACK_STATE_IDLE;
   } else {
     commit_state_ = COMMIT_STATE_IDLE;
     SetNeedsCommit();
@@ -441,11 +612,40 @@ void SchedulerStateMachine::DidLoseOutputSurface() {
   output_surface_state_ = OUTPUT_SURFACE_LOST;
 }
 
-void SchedulerStateMachine::SetHasPendingTree(bool has_pending_tree) {
+void SchedulerStateMachine::SetHasTrees(bool has_pending_tree,
+                                        bool active_tree_is_null) {
+  if (has_pending_tree_ && !has_pending_tree) {
+    // This is a new activation.
+    VLOG(0) << __LINE__ << "ACTIVATED!\n";
+    draw_attempt_count_++;
+    active_tree_has_been_drawn_ = false;
+
+    if (draw_if_possible_failed_)
+      last_begin_frame_count_draw_was_called_ = -1;
+
+    if (COMMIT_STATE_WAITING_FOR_ACTIVATION == commit_state_) {
+      if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION) {
+        commit_state_ = COMMIT_STATE_WAITING_FOR_FIRST_FORCED_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_FORCED_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;
+      }
+    }
+  }
+
   has_pending_tree_ = has_pending_tree;
+  active_tree_is_null_ = active_tree_is_null;
 }
 
-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);