Revert of Tab/Desktop Capture: Use requests instead of timer-based refreshing.

media/capture/content/smooth_event_sampler.cc

 // Copyright (c) 2015 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 "media/capture/content/smooth_event_sampler.h"
 
 #include <stdint.h>
 
 #include <algorithm>
 
 #include "base/trace_event/trace_event.h"
 
 namespace media {
 
-SmoothEventSampler::SmoothEventSampler(base::TimeDelta min_capture_period)
-    : token_bucket_(base::TimeDelta::Max()) {
+SmoothEventSampler::SmoothEventSampler(base::TimeDelta min_capture_period,
+                                       int redundant_capture_goal)
+    : redundant_capture_goal_(redundant_capture_goal),
+      overdue_sample_count_(0),
+      token_bucket_(base::TimeDelta::Max()) {
   SetMinCapturePeriod(min_capture_period);
 }
 
 void SmoothEventSampler::SetMinCapturePeriod(base::TimeDelta period) {
   DCHECK_GT(period, base::TimeDelta());
   min_capture_period_ = period;
   token_bucket_capacity_ = period + period / 2;
   token_bucket_ = std::min(token_bucket_capacity_, token_bucket_);
 }
 
@@ skipping 22 matching lines @@
   return token_bucket_ >= min_capture_period_;
 }
 
 void SmoothEventSampler::RecordSample() {
   token_bucket_ -= min_capture_period_;
   if (token_bucket_ < base::TimeDelta())
     token_bucket_ = base::TimeDelta();
   TRACE_COUNTER1("gpu.capture", "MirroringTokenBucketUsec",
                  std::max<int64_t>(0, token_bucket_.InMicroseconds()));
 
-  if (HasUnrecordedEvent())
+  if (HasUnrecordedEvent()) {
     last_sample_ = current_event_;
+    overdue_sample_count_ = 0;
+  } else {
+    ++overdue_sample_count_;
+  }
+}
+
+bool SmoothEventSampler::IsOverdueForSamplingAt(
+    base::TimeTicks event_time) const {
+  DCHECK(!event_time.is_null());
+
+  if (!HasUnrecordedEvent() && overdue_sample_count_ >= redundant_capture_goal_)
+    return false;  // Not dirty.
+
+  if (last_sample_.is_null())
+    return true;
+
+  // If we're dirty but not yet old, then we've recently gotten updates, so we
+  // won't request a sample just yet.
+  base::TimeDelta dirty_interval = event_time - last_sample_;
+  return dirty_interval >=
+         base::TimeDelta::FromMilliseconds(OVERDUE_DIRTY_THRESHOLD_MILLIS);
 }
 
 bool SmoothEventSampler::HasUnrecordedEvent() const {
   return !current_event_.is_null() && current_event_ != last_sample_;
 }
 
 }  // namespace media