cc: Add MainAndImplFrameTimeDelta UMA.

cc/scheduler/scheduler_state_machine.cc

 // Copyright 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/scheduler/scheduler_state_machine.h"
 
 #include "base/format_macros.h"
 #include "base/logging.h"
 #include "base/strings/stringprintf.h"
 #include "base/trace_event/trace_event.h"
@@ skipping 595 matching lines @@
       output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
     }
   }
 
   // Update state if there's no updates heading for the active tree, but we need
   // to do a forced draw.
   if (commit_has_no_updates &&
       forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW) {
     DCHECK(!has_pending_tree_);
     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;
 
   last_commit_had_no_updates_ = commit_has_no_updates;
 }
 
 void SchedulerStateMachine::WillActivate() {
   if (begin_main_frame_state_ ==
       BEGIN_MAIN_FRAME_STATE_WAITING_FOR_ACTIVATION) {
     begin_main_frame_state_ = settings_.commit_to_active_tree
                                   ? BEGIN_MAIN_FRAME_STATE_WAITING_FOR_DRAW
                                   : BEGIN_MAIN_FRAME_STATE_IDLE;
   }
 
   if (output_surface_state_ == OUTPUT_SURFACE_WAITING_FOR_FIRST_ACTIVATION)
     output_surface_state_ = OUTPUT_SURFACE_ACTIVE;
 
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_ACTIVATION)
     forced_redraw_state_ = FORCED_REDRAW_STATE_WAITING_FOR_DRAW;
 
   has_pending_tree_ = false;
   pending_tree_is_ready_for_activation_ = false;
   active_tree_needs_first_draw_ = true;
   needs_redraw_ = true;
 }
 
 void SchedulerStateMachine::WillDrawInternal() {
+  // If a new active tree is pending after the one we are about to draw,
+  // the main thread is in a high latency mode.
+  // main_thread_missed_last_deadline_ is here in addition to
+  // OnBeginImplFrameIdle for cases where the scheduler aborts draws outside
+  // of the deadline.
+  main_thread_missed_last_deadline_ = CommitPending() || has_pending_tree_;

[brianderson, 2016/02/19 01:52:17]

Need to add a unit test for this, but probably won't split it out to a separate
patch this time.

I think this could cause us to unintentionally recover main latency when
can_draw_ goes from false to true.

Without this line, the HudWithRootLayerChange was failing the following DCHECK
in CompositorTimingHistory:

DCHECK_EQ(main_thread_missed_last_deadline,
                !main_and_impl_delta.is_zero());

+
   // We need to reset needs_redraw_ before we draw since the
   // draw itself might request another draw.
   needs_redraw_ = false;
 
   draw_funnel_ = true;
   active_tree_needs_first_draw_ = false;
   did_draw_in_last_frame_ = true;
   last_frame_number_draw_performed_ = current_frame_number_;
 
   if (forced_redraw_state_ == FORCED_REDRAW_STATE_WAITING_FOR_DRAW)
@@ skipping 480 matching lines @@
     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