[WIP] Move media/capture to device/capture

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()) {
-  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_);
-}
-
-void SmoothEventSampler::ConsiderPresentationEvent(base::TimeTicks event_time) {
-  DCHECK(!event_time.is_null());
-
-  // Add tokens to the bucket based on advancement in time.  Then, re-bound the
-  // number of tokens in the bucket.  Overflow occurs when there is too much
-  // time between events (a common case), or when RecordSample() is not being
-  // called often enough (a bug).  On the other hand, if RecordSample() is being
-  // called too often (e.g., as a reaction to IsOverdueForSamplingAt()), the
-  // bucket will underflow.
-  if (!current_event_.is_null()) {
-    if (current_event_ < event_time) {
-      token_bucket_ += event_time - current_event_;
-      if (token_bucket_ > token_bucket_capacity_)
-        token_bucket_ = token_bucket_capacity_;
-    }
-    TRACE_COUNTER1("gpu.capture", "MirroringTokenBucketUsec",
-                   std::max<int64_t>(0, token_bucket_.InMicroseconds()));
-  }
-  current_event_ = event_time;
-}
-
-bool SmoothEventSampler::ShouldSample() const {
-  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())
-    last_sample_ = current_event_;
-}
-
-bool SmoothEventSampler::HasUnrecordedEvent() const {
-  return !current_event_.is_null() && current_event_ != last_sample_;
-}
-
-}  // namespace media