cc: Implement deadine scheduling disabled by default

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/values.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),
       forced_redraw_state_(FORCED_REDRAW_STATE_IDLE),
       readback_state_(READBACK_STATE_IDLE),
       commit_count_(0),
-      current_frame_number_(0),
-      last_frame_number_where_begin_frame_sent_to_main_thread_(-1),
-      last_frame_number_swap_performed_(-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),
       needs_redraw_(false),
       swap_used_incomplete_tile_(false),
       needs_commit_(false),
       main_thread_needs_layer_textures_(false),
-      inside_begin_frame_(false),
       visible_(false),
       can_start_(false),
       can_draw_(false),
       has_pending_tree_(false),
       pending_tree_is_ready_for_activation_(false),
       active_tree_needs_first_draw_(false),
       draw_if_possible_failed_(false),
       did_create_and_initialize_first_output_surface_(false) {}
 
 const char* SchedulerStateMachine::OutputSurfaceStateToString(
     OutputSurfaceState state) {
   switch (state) {
     case OUTPUT_SURFACE_ACTIVE:
       return "OUTPUT_SURFACE_ACTIVE";
     case OUTPUT_SURFACE_LOST:
       return "OUTPUT_SURFACE_LOST";
     case OUTPUT_SURFACE_CREATING:
       return "OUTPUT_SURFACE_CREATING";
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT";
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
       return "OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION";
   }
   NOTREACHED();
   return "???";
 }
 
+const char* SchedulerStateMachine::BeginFrameStateToString(
+    BeginFrameState state) {
+  switch (state) {
+    case BEGIN_FRAME_STATE_IDLE:
+      return "BEGIN_FRAME_STATE_IDLE";
+    case BEGIN_FRAME_STATE_INSIDE_BEGIN_FRAME:
+      return "BEGIN_FRAME_STATE_INSIDE_BEGIN_FRAME";
+    case BEGIN_FRAME_STATE_DEADLINE_PENDING:
+      return "BEGIN_FRAME_STATE_DEADLINE_PENDING";
+    case BEGIN_FRAME_STATE_INSIDE_DEADLINE:
+      return "BEGIN_FRAME_STATE_INSIDE_DEADLINE";
+  }
+  NOTREACHED();
+  return "???";
+}
+
 const char* SchedulerStateMachine::CommitStateToString(CommitState state) {
   switch (state) {
     case COMMIT_STATE_IDLE:
       return "COMMIT_STATE_IDLE";
     case COMMIT_STATE_FRAME_IN_PROGRESS:
       return "COMMIT_STATE_FRAME_IN_PROGRESS";
     case COMMIT_STATE_READY_TO_COMMIT:
       return "COMMIT_STATE_READY_TO_COMMIT";
     case COMMIT_STATE_WAITING_FOR_FIRST_DRAW:
       return "COMMIT_STATE_WAITING_FOR_FIRST_DRAW";
@@ skipping 80 matching lines @@
   }
   NOTREACHED();
   return "???";
 }
 
 scoped_ptr<base::Value> SchedulerStateMachine::AsValue() const  {
   scoped_ptr<base::DictionaryValue> state(new base::DictionaryValue);
 
   scoped_ptr<base::DictionaryValue> major_state(new base::DictionaryValue);
   major_state->SetString("next_action", ActionToString(NextAction()));
+  major_state->SetString("commit_state",

[enne (OOO), 2013/09/10 03:35:44]

begin_frame_state

[brianderson, 2013/09/10 21:16:56]

Done.

+                         BeginFrameStateToString(begin_frame_state_));
   major_state->SetString("commit_state", CommitStateToString(commit_state_));
   major_state->SetString("texture_state_",
                          TextureStateToString(texture_state_));
   major_state->SetString("output_surface_state_",
                          OutputSurfaceStateToString(output_surface_state_));
   major_state->SetString(
       "forced_redraw_state",
       ForcedRedrawOnTimeoutStateToString(forced_redraw_state_));
   major_state->SetString("readback_state",
                          SynchronousReadbackStateToString(readback_state_));
@@ skipping 21 matching lines @@
       (last_begin_frame_args_.frame_time - base::TimeTicks()).InMicroseconds() /
           1000.0L);
   timestamps_state->SetDouble(
       "6_deadline",
       (last_begin_frame_args_.deadline - base::TimeTicks()).InMicroseconds() /
           1000.0L);
   state->Set("major_timestamps_in_ms", timestamps_state.release());
 
   scoped_ptr<base::DictionaryValue> minor_state(new base::DictionaryValue);
   minor_state->SetInteger("commit_count", commit_count_);
-  minor_state->SetInteger("current_frame_number", current_frame_number_);
+  minor_state->SetInteger("begin_frame_count_", begin_frame_count_);
+  minor_state->SetInteger("draw_attempt_count_", draw_attempt_count_);
+
+  minor_state->SetInteger("last_begin_frame_count_swap_performed_",
+                          last_begin_frame_count_swap_performed_);
+  minor_state->SetInteger("last_draw_attempt_count_draw_was_called_",
+                          last_draw_attempt_count_draw_was_called_);
   minor_state->SetInteger(
-      "last_frame_number_where_begin_frame_sent_to_main_thread",
-      last_frame_number_where_begin_frame_sent_to_main_thread_);
-  minor_state->SetInteger("last_frame_number_swap_performed_",
-                          last_frame_number_swap_performed_);
+      "last_begin_frame_count_begin_frame_sent_to_main_thread_",
+      last_begin_frame_count_begin_frame_sent_to_main_thread_);
+  minor_state->SetInteger("last_draw_attempt_count_tree_activation_attempted_",
+                          last_draw_attempt_count_tree_activation_attempted_);
   minor_state->SetInteger(
-      "last_frame_number_where_update_visible_tiles_was_called",
-      last_frame_number_where_update_visible_tiles_was_called_);
-  minor_state->SetInteger("consecutive_failed_draws",
+      "last_draw_attempt_count_update_visible_tiles_was_called_",
+      last_draw_attempt_count_update_visible_tiles_was_called_);
+
+  minor_state->SetInteger("consecutive_failed_draws_",
                           consecutive_failed_draws_);
   minor_state->SetBoolean("needs_redraw", needs_redraw_);
   minor_state->SetBoolean("swap_used_incomplete_tile",
                           swap_used_incomplete_tile_);
   minor_state->SetBoolean("needs_commit", needs_commit_);
   minor_state->SetBoolean("main_thread_needs_layer_textures",
                           main_thread_needs_layer_textures_);
-  minor_state->SetBoolean("inside_begin_frame", inside_begin_frame_);
   minor_state->SetBoolean("visible", visible_);
   minor_state->SetBoolean("can_start", can_start_);
   minor_state->SetBoolean("can_draw", can_draw_);
   minor_state->SetBoolean("has_pending_tree", has_pending_tree_);
   minor_state->SetBoolean("pending_tree_is_ready_for_activation_",
                           pending_tree_is_ready_for_activation_);
   minor_state->SetBoolean("active_tree_needs_first_draw_",
                           active_tree_needs_first_draw_);
   minor_state->SetBoolean("draw_if_possible_failed", draw_if_possible_failed_);
   minor_state->SetBoolean("did_create_and_initialize_first_output_surface",
                           did_create_and_initialize_first_output_surface_);
   state->Set("minor_state", minor_state.release());
 
   return state.PassAs<base::Value>();
 }
 
-bool SchedulerStateMachine::HasDrawnAndSwappedThisFrame() const {
-  return current_frame_number_ == last_frame_number_swap_performed_;
+bool SchedulerStateMachine::HasSwappedThisFrame() const {
+  return begin_frame_count_ == last_begin_frame_count_swap_performed_;
 }
 
-bool SchedulerStateMachine::HasUpdatedVisibleTilesThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_update_visible_tiles_was_called_;
+bool SchedulerStateMachine::HasDrawnThisDrawAttempt() const {
+  return draw_attempt_count_ == last_draw_attempt_count_draw_was_called_;
 }
 
 bool SchedulerStateMachine::HasSentBeginFrameToMainThreadThisFrame() const {
-  return current_frame_number_ ==
-         last_frame_number_where_begin_frame_sent_to_main_thread_;
+  return begin_frame_count_ ==
+         last_begin_frame_count_begin_frame_sent_to_main_thread_;
+}
+
+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_;
 }
 
 bool SchedulerStateMachine::PendingDrawsShouldBeAborted() const {
   // These are all the cases where we normally cannot or do not want to draw
   // but, if needs_redraw_ is true and we do not draw to make forward progress,
   // we might deadlock with the main thread.
   // This should be a superset of PendingActivationsShouldBeForced() since
   // activation of the pending tree is blocked by drawing of the active tree and
   // the main thread might be blocked on activation of the most recent commit.
   if (PendingActivationsShouldBeForced())
@@ skipping 42 matching lines @@
   // readback.
   if (active_tree_needs_first_draw_ || has_pending_tree_)
     return false;
 
   // We need to create the output surface if we don't have one and we haven't
   // started creating one yet.
   return output_surface_state_ == OUTPUT_SURFACE_LOST;
 }
 
 bool SchedulerStateMachine::ShouldDraw() const {
+  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_WAITING_FOR_REPLACEMENT_COMMIT ||
       readback_state_ == READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION)
     return false;
 
   // Draw immediately for readbacks to unblock the main thread quickly.
   if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK) {
     DCHECK_EQ(commit_state_, COMMIT_STATE_WAITING_FOR_FIRST_DRAW);
     return true;
   }
 
   // If we need to abort draws, we should do so ASAP since the draw could
   // be blocking other important actions (like output surface initialization),
   // from occuring. If we are waiting for the first draw, then perfom the
   // aborted draw to keep things moving. If we are not waiting for the first
   // draw however, we don't want to abort for no reason.
   if (PendingDrawsShouldBeAborted())
     return active_tree_needs_first_draw_;
 
-  // After this line, we only want to draw once per frame.
-  if (HasDrawnAndSwappedThisFrame())
+  // After this line, we only want to swap once per frame.
+  if (HasSwappedThisFrame())
     return false;
 
-  // We currently only draw within the BeginFrame.
-  if (!inside_begin_frame_)
+  // 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;
   }
 
   return needs_redraw_;
 }
 
 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);
   return false;
 }
 
 bool SchedulerStateMachine::ShouldActivatePendingTree() const {
   // There is nothing to activate.
   if (!has_pending_tree_)
     return false;
+  if (HasActivatedPendingTreeThisDrawAttempt())
+    return false;
 
   // We should not activate a second tree before drawing the first one.
   // Even if we need to force activation of the pending tree, we should abort
   // drawing the active tree first.
   if (active_tree_needs_first_draw_)
     return false;
 
   // If we want to force activation, do so ASAP.
   if (PendingActivationsShouldBeForced())
     return true;
 
   // At this point, only activate if we are ready to activate.
   return pending_tree_is_ready_for_activation_;
 }
 
 bool SchedulerStateMachine::ShouldUpdateVisibleTiles() const {
   if (!settings_.impl_side_painting)
     return false;
-  if (HasUpdatedVisibleTilesThisFrame())
+  if (HasUpdatedVisibleTilesThisDrawAttempt())
     return false;
 
   // There's no reason to check for tiles if we don't have an output surface.
   if (!HasInitializedOutputSurface())
     return false;
 
   // We always want to update the most recent visible tiles before drawing
   // so we draw with fewer missing tiles.
   if (ShouldDraw())
     return true;
@@ skipping 20 matching lines @@
     return false;
 
   // We want to handle readback commits immediately to unblock the main thread.
   // Note: This BeginFrame will correspond to the replacement commit that comes
   // after the readback commit itself, so we only send the BeginFrame if a
   // commit isn't already pending behind the readback.
   if (readback_state_ == READBACK_STATE_NEEDS_BEGIN_FRAME)
     return !CommitPending();
 
   // We do not need commits if we are not visible, unless there's a
-  // request for a forced commit.
+  // request for a readback.
   if (!visible_)
     return false;
 
+  // We shouldn't normally accept commits if there isn't an OutputSurface.
+  if (!HasInitializedOutputSurface())
+    return false;
+
   // We want to start the first commit after we get a new output surface ASAP.
   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_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;

[enne (OOO), 2013/09/10 03:35:44]

Can you rephrase this comment to refer to this "return false" and not to the
"return true" at the end of this function? In this case, it seems like you don't
send a begin frame to the main thread if you are already waiting on a begin
frame to the compositor thread, since you'll do it then.  (Or, am I
misunderstanding?)

[brianderson, 2013/09/10 21:16:56]

I will change the comment to refer to the "return fals". Also, I don't think the
BeginFrameNeededByImplThread is needed here anymore since the conditions that
come beforehand allow us to make forward progress in all the cases that we need
it explicitly now.

+
   // We need a new commit for the forced redraw. This honors the
   // single commit per interval because the result will be swapped to screen.
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_COMMIT)
     return true;
 
   // After this point, we only start a commit once per frame.
   if (HasSentBeginFrameToMainThreadThisFrame())
     return false;
 
-  // We shouldn't normally accept commits if there isn't an OutputSurface.
-  if (!HasInitializedOutputSurface())
-    return false;
-
   return true;
 }
 
 bool SchedulerStateMachine::ShouldCommit() const {
   return commit_state_ == COMMIT_STATE_READY_TO_COMMIT;
 }
 
 SchedulerStateMachine::Action SchedulerStateMachine::NextAction() const {
   if (ShouldAcquireLayerTexturesForMainThread())
     return ACTION_ACQUIRE_LAYER_TEXTURES_FOR_MAIN_THREAD;
@@ skipping 26 matching lines @@
   DCHECK(!(forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW &&
            readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK));
 }
 
 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:
       UpdateStateOnActivation();
       return;
 
     case ACTION_SEND_BEGIN_FRAME_TO_MAIN_THREAD:
       DCHECK(!has_pending_tree_);
       DCHECK(visible_ || readback_state_ == READBACK_STATE_NEEDS_BEGIN_FRAME);
       commit_state_ = COMMIT_STATE_FRAME_IN_PROGRESS;
       needs_commit_ = false;
       if (readback_state_ == READBACK_STATE_NEEDS_BEGIN_FRAME)
         readback_state_ = READBACK_STATE_WAITING_FOR_COMMIT;
-      last_frame_number_where_begin_frame_sent_to_main_thread_ =
-          current_frame_number_;
+      last_begin_frame_count_begin_frame_sent_to_main_thread_ =
+          begin_frame_count_;
       return;
 
     case ACTION_COMMIT: {
       bool commit_was_aborted = false;
       UpdateStateOnCommit(commit_was_aborted);
       return;
     }
 
     case ACTION_DRAW_AND_SWAP_FORCED:
     case ACTION_DRAW_AND_SWAP_IF_POSSIBLE: {
@@ skipping 23 matching lines @@
 
     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::UpdateStateOnCommit(bool commit_was_aborted) {
   commit_count_++;
+  draw_attempt_count_++;

[enne (OOO), 2013/09/10 03:35:44]

What's the difference between "draw attempt" and "source frame"?  I have to
admit that I'm a bit ಠ_ಠ of how this generates the confusing function name
HasDrawnThisDrawAttempt.

It also seems to me like you shouldn't bump the draw attempt count in both
commit and activation (and begin frame too?).  In impl-side painting for
example, commit shouldn't affect drawing state.

[brianderson, 2013/09/10 21:16:56]

Note: It is possible for a readback and a swap to occur within the same
BeginImplFrame interval, which was the initial reason to use two different
counters.

begin_frame_count_ is used to block anything that should only be done once per
BeginImplFrame, which include A) swaps and B) sending BeginMainFrames.

draw_attempt_count_ is used to block actions that shouldn't be called more than
once in a series of back-to-back actions within ProcessScheduledActions, which
include 1) readbacks, 2) updating visible tiles, and 3) activating the pending
tree.

With the new code base, however, I think I can get rid of draw_attempt_count,
because there are other mechanisms that will prevent us from doing 1 and 3
multiple times now: 1) The readback state will only draw in a single sate; 3)
Activation will always occur now, blocking subsequent activations until the
active tree has been drawn

For 2, I'm trying to see if I can get rid of
HasUpdatedVisibleTilesThisDrawAttempt. I think I can if I only call it when the
last swap used an imcomplete tile, in which case I can change the name to
HasUpdatedVisibleTilesThisFrame.

 
   // If we are impl-side-painting but the commit was aborted, then we behave
   // mostly as if we are not impl-side-painting since there is no pending tree.
   has_pending_tree_ = settings_.impl_side_painting && !commit_was_aborted;
 
   // Update state related to readbacks.
   if (readback_state_ == READBACK_STATE_WAITING_FOR_COMMIT) {
     // Update the state if this is the readback commit.
     readback_state_ = has_pending_tree_
                           ? READBACK_STATE_WAITING_FOR_ACTIVATION
@@ skipping 49 matching lines @@
       (!commit_was_aborted ||
        readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK ||
        forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)) {
     needs_redraw_ = true;
     active_tree_needs_first_draw_ = true;
   }
 
   // This post-commit work is common to both completed and aborted commits.
   pending_tree_is_ready_for_activation_ = false;
 
-  if (draw_if_possible_failed_)
-    last_frame_number_swap_performed_ = -1;
+  if (draw_if_possible_failed_) {
+    last_begin_frame_count_swap_performed_ = -1;
+    last_draw_attempt_count_draw_was_called_ = -1;
+  }
 
   // If we are planing to draw with the new commit, lock the layer textures for
   // use on the impl thread. Otherwise, leave them unlocked.
   if (has_pending_tree_ || needs_redraw_)
     texture_state_ = LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD;
   else
     texture_state_ = LAYER_TEXTURE_STATE_UNLOCKED;
 }
 
 void SchedulerStateMachine::UpdateStateOnActivation() {
+  draw_attempt_count_++;
+
   // Update output surface state.
   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 
   // Update readback state
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 
   // Update forced redraw state
   if (readback_state_ == READBACK_STATE_WAITING_FOR_ACTIVATION)
     readback_state_ = READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK;
   else if (readback_state_ == READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION)
     readback_state_ = READBACK_STATE_IDLE;
 
   has_pending_tree_ = false;
   pending_tree_is_ready_for_activation_ = false;
   active_tree_needs_first_draw_ = true;
   needs_redraw_ = true;
+  last_draw_attempt_count_tree_activation_attempted_ = draw_attempt_count_;
 }
 
 void SchedulerStateMachine::UpdateStateOnDraw(bool did_swap) {
   DCHECK(readback_state_ != READBACK_STATE_WAITING_FOR_REPLACEMENT_COMMIT &&
          readback_state_ != READBACK_STATE_WAITING_FOR_REPLACEMENT_ACTIVATION)
       << *AsValue();
 
   if (readback_state_ == READBACK_STATE_WAITING_FOR_DRAW_AND_READBACK) {
     // The draw correspons to a readback commit.
     DCHECK_EQ(commit_state_, COMMIT_STATE_WAITING_FOR_FIRST_DRAW);
@@ skipping 12 matching lines @@
              !has_pending_tree_) {
     commit_state_ = COMMIT_STATE_IDLE;
   }
 
   if (texture_state_ == LAYER_TEXTURE_STATE_ACQUIRED_BY_IMPL_THREAD)
     texture_state_ = LAYER_TEXTURE_STATE_UNLOCKED;
 
   needs_redraw_ = false;
   draw_if_possible_failed_ = false;
   active_tree_needs_first_draw_ = false;
+  last_draw_attempt_count_draw_was_called_ = draw_attempt_count_;
 
   if (did_swap) {
     swap_used_incomplete_tile_ = false;
-    last_frame_number_swap_performed_ = current_frame_number_;
+    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;

[enne (OOO), 2013/09/10 03:35:44]

Just so I understand this correctly, this is the normal (only?) mechanism for
going from BEGIN_FRAME_STATE_INSIDE_DEADLINE to BEGIN_FRAME_STATE_IDLE?

[brianderson, 2013/09/10 21:16:56]

Yes, this is the only way.  We only transition out of
BEGIN_FRAME_STATE_INSIDE_DEADLINE when all actions that occur back-to-back in
response to entering BEGIN_FRAME_STATE_INSIDE_DEADLINE have completed. This is
important because actions after the draw, such as activation and subsequently
sending BeginFrame to the main thread, can occur inside
BEGIN_FRAME_STATE_INSIDE_DEADLINE.  (Sending the BeginFrame to the main thread
will not occur in BEGIN_FRAME_STATE_IDLE.)

I will add a comment.

+      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() ||
+         ProactiveBeginFrameWantedByImplThread();
+}
+
 // These are the cases where we definitely (or almost definitely) have a
 // new frame to draw and can draw.
 bool SchedulerStateMachine::BeginFrameNeededToDrawByImplThread() const {
   // The output surface is the provider of BeginFrames for the impl thread,
   // so we are not going to get them even if we ask for them.
   if (!HasInitializedOutputSurface())
     return false;
 
   // If we can't draw, don't tick until we are notified that we can draw again.
   if (!can_draw_)
@@ skipping 14 matching lines @@
   if (swap_used_incomplete_tile_)
     return true;
 
   return needs_redraw_;
 }
 
 // These are cases where we are very likely to draw soon, but might not
 // actually have a new frame to draw when we receive the next BeginFrame.
 // Proactively requesting the BeginFrame helps hide the round trip latency of
 // the SetNeedsBeginFrame request that has to go to the Browser.
-// However, this is bad for the synchronous compositor because we have to
-// draw when we get the BeginFrame and could end up drawing many duplicate
-// frames.
 bool SchedulerStateMachine::ProactiveBeginFrameWantedByImplThread() const {
   // The output surface is the provider of BeginFrames for the impl thread,
   // so we are not going to get them even if we ask for them.
   if (!HasInitializedOutputSurface())
     return false;
 
+  // Proactive BeginFrames are bad for the synchronous compositor because we
+  // have to draw when we get the BeginFrame and could end up drawing many
+  // duplicate frames if our new frame isn't ready in time.
+  if (settings_.using_synchronous_renderer_compositor)
+    return false;
+
+  // Do not be proactive if vsync is off.
+  if (!settings_.throttle_frame_production)
+    return false;
+
   // Do not be proactive when invisible.
   if (!visible_)
     return false;
 
   // We should proactively request a BeginFrame if a commit is pending
   // because we will want to draw if the commit completes quickly.
   if (needs_commit_ || commit_state_ != COMMIT_STATE_IDLE)
     return true;
 
   // If the pending tree activates quickly, we'll want a BeginFrame soon
   // to draw the new active tree.
   if (has_pending_tree_)
     return true;
 
   return false;
 }
 
-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_needs_first_draw_;
+}
+
+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);

[enne (OOO), 2013/09/10 03:35:44]

What guarantees that this is true? It seems like you only get to
BEGIN_FRAME_STATE_DEADLINE_PENDING via AdvanceBeginFrameStateWhenNoActionsRemain
and that seems like it would race with this PostTask-initiated event.

[brianderson, 2013/09/10 21:16:56]

In Scheduler::BeginFrame, we will always transition to the
BEGIN_FRAME_STATE_DEADLINE_PENDING at the end of the call to
ProcessScheduledActions, which will alway happen before any posted tasks. I
suppose I could make that transition explicit rather than relying on
AdvanceBeginFrameStateWhenNoActionsRemain.

Now that I think about it, I should get rid of
AdvanceBeginFrameStateWhenNoActionsRemain altoghether by also transitioning to
BEGIN_FRAME_STATE_IDLE explicitly at the end of Scheduler::OnBeginFrameDeadline.

I really wanted to get rid of AdvanceBeginFrameStateWhenNoActionsRemain, but
couldn't figure out how in older versions of this patch.

+  draw_attempt_count_++;
+  begin_frame_state_ = BEGIN_FRAME_STATE_INSIDE_DEADLINE;
 }
 
 void SchedulerStateMachine::SetVisible(bool visible) { visible_ = visible; }
 
+void SchedulerStateMachine::SetCanDraw(bool can_draw) { can_draw_ = can_draw; }
+
 void SchedulerStateMachine::SetNeedsRedraw() { needs_redraw_ = true; }
 
 void SchedulerStateMachine::DidSwapUseIncompleteTile() {
   swap_used_incomplete_tile_ = true;
 }
 
 void SchedulerStateMachine::DidDrawIfPossibleCompleted(bool success) {
   draw_if_possible_failed_ = !success;
   if (draw_if_possible_failed_) {
     needs_redraw_ = true;
@@ skipping 58 matching lines @@
     return;
   output_surface_state_ = OUTPUT_SURFACE_LOST;
   needs_redraw_ = false;
 }
 
 void SchedulerStateMachine::NotifyReadyToActivate() {
   if (has_pending_tree_)
     pending_tree_is_ready_for_activation_ = true;
 }
 
-void SchedulerStateMachine::SetCanDraw(bool can) { can_draw_ = can; }
-
 void SchedulerStateMachine::DidCreateAndInitializeOutputSurface() {
   DCHECK_EQ(output_surface_state_, OUTPUT_SURFACE_CREATING);
   output_surface_state_ = OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT;
 
   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?
     needs_commit_ = true;
   }
   did_create_and_initialize_first_output_surface_ = true;
 }
 
 bool SchedulerStateMachine::HasInitializedOutputSurface() const {
   switch (output_surface_state_) {
     case OUTPUT_SURFACE_LOST:
     case OUTPUT_SURFACE_CREATING:
       return false;
 
     case OUTPUT_SURFACE_ACTIVE:
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_COMMIT:
     case OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION:
       return true;
   }
   NOTREACHED();
   return false;
 }
 
 }  // namespace cc