cc: Add info for DCHECK in DBTS::NextTickTarget

cc/scheduler/delay_based_time_source.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/delay_based_time_source.h"
 
 #include <algorithm>
 #include <cmath>
 
 #include "base/debug/trace_event.h"
@@ skipping 194 matching lines @@
 //      now=37   tick_target=16.667  new_target=50.000  -->
 //          tick(), PostDelayedTask(floor(50.000-37)) --> PostDelayedTask(13)
 base::TimeTicks DelayBasedTimeSource::NextTickTarget(base::TimeTicks now) {
   base::TimeDelta new_interval = next_parameters_.interval;
   int intervals_elapsed =
       static_cast<int>(floor((now - next_parameters_.tick_target).InSecondsF() /
                              new_interval.InSecondsF()));
   base::TimeTicks last_effective_tick =
       next_parameters_.tick_target + new_interval * intervals_elapsed;
   base::TimeTicks new_tick_target = last_effective_tick + new_interval;
-  DCHECK(new_tick_target > now);
+  DCHECK(now < new_tick_target)
+      << "now = " << now.ToInternalValue()
+      << "; new_tick_target = " << new_tick_target.ToInternalValue()
+      << "; new_interval = " << new_interval.InMicroseconds()
+      << "; tick_target = " << next_parameters_.tick_target.ToInternalValue()
+      << "; intervals_elapsed = " << intervals_elapsed
+      << "; last_effective_tick = " << last_effective_tick.ToInternalValue();
 
   // Avoid double ticks when:
   // 1) Turning off the timer and turning it right back on.
   // 2) Jittery data is passed to SetTimebaseAndInterval().
   if (new_tick_target - last_tick_time_ <=
       new_interval / static_cast<int>(1.0 / kDoubleTickThreshold))
     new_tick_target += new_interval;
 
   return new_tick_target;
 }
 
 void DelayBasedTimeSource::PostNextTickTask(base::TimeTicks now) {
   base::TimeTicks new_tick_target = NextTickTarget(now);
 
   // Post another task *before* the tick and update state
   base::TimeDelta delay = new_tick_target - now;
   DCHECK(delay.InMillisecondsF() <=
          next_parameters_.interval.InMillisecondsF() *
          (1.0 + kDoubleTickThreshold));
   thread_->PostDelayedTask(base::Bind(&DelayBasedTimeSource::OnTimerFired,
                                       weak_factory_.GetWeakPtr()),
                            delay);
 
   next_parameters_.tick_target = new_tick_target;
   current_parameters_ = next_parameters_;
 }
 
 }  // namespace cc