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

media/capture/content/video_capture_oracle.cc

Index: media/capture/content/video_capture_oracle.cc
diff --git a/media/capture/content/video_capture_oracle.cc b/media/capture/content/video_capture_oracle.cc
index e8dd752e9f453062f56c411acc9fc377176098e6..a363987d51799a5512940711416a7c93f79b0808 100644
--- a/media/capture/content/video_capture_oracle.cc
+++ b/media/capture/content/video_capture_oracle.cc
@@ -14,13 +14,16 @@
 
 namespace {
 
-// When a non-compositor event arrives after animation has halted, this
-// controls how much time must elapse before deciding to allow a capture.
-const int kAnimationHaltPeriodBeforeOtherSamplingMicros = 250000;
-
-// When estimating frame durations, this is the hard upper-bound on the
-// estimate.
-const int kUpperBoundDurationEstimateMicros = 1000000;  // 1 second
+// This value controls how many redundant, timer-base captures occur when the
+// content is static. Redundantly capturing the same frame allows iterative
+// quality enhancement, and also allows the buffer to fill in "buffered mode".
+//
+// TODO(nick): Controlling this here is a hack and a layering violation, since
+// it's a strategy specific to the WebRTC consumer, and probably just papers
+// over some frame dropping and quality bugs. It should either be controlled at
+// a higher level, or else redundant frame generation should be pushed down
+// further into the WebRTC encoding stack.
+const int kNumRedundantCapturesOfStaticContent = 200;
 
 // The half-life of data points provided to the accumulator used when evaluating
 // the recent utilization of the buffer pool.  This value is based on a
@@ -103,7 +106,8 @@
       next_frame_number_(0),
       last_successfully_delivered_frame_number_(-1),
       num_frames_pending_(0),
-      smoothing_sampler_(min_capture_period),
+      smoothing_sampler_(min_capture_period,
+                         kNumRedundantCapturesOfStaticContent),
       content_sampler_(min_capture_period),
       resolution_chooser_(max_frame_size, resolution_change_policy),
       buffer_pool_utilization_(base::TimeDelta::FromMicroseconds(
@@ -160,21 +164,20 @@
       break;
     }
 
-    case kActiveRefreshRequest:
-    case kPassiveRefreshRequest:
+    case kTimerPoll:
+      // While the timer is firing, only allow a sampling if there are none
+      // currently in-progress.
+      if (num_frames_pending_ == 0)
+        should_sample = smoothing_sampler_.IsOverdueForSamplingAt(event_time);
+      break;
+
     case kMouseCursorUpdate:
-      // Only allow non-compositor samplings when content has not recently been
-      // animating, and only if there are no samplings currently in progress.
+      // Only allow a sampling if there are none currently in-progress.
       if (num_frames_pending_ == 0) {
-        if (!content_sampler_.HasProposal() ||
-            ((event_time - last_time_animation_was_detected_).InMicroseconds() >
-             kAnimationHaltPeriodBeforeOtherSamplingMicros)) {
-          smoothing_sampler_.ConsiderPresentationEvent(event_time);
-          should_sample = smoothing_sampler_.ShouldSample();
-        }
+        smoothing_sampler_.ConsiderPresentationEvent(event_time);
+        should_sample = smoothing_sampler_.ShouldSample();
       }
       break;
-
     case kNumEvents:
       NOTREACHED();
       break;
@@ -190,8 +193,8 @@
       duration_of_next_frame_ =
           event_time - GetFrameTimestamp(next_frame_number_ - 1);
     }
-    const base::TimeDelta upper_bound =
-        base::TimeDelta::FromMilliseconds(kUpperBoundDurationEstimateMicros);
+    const base::TimeDelta upper_bound = base::TimeDelta::FromMilliseconds(
+        SmoothEventSampler::OVERDUE_DIRTY_THRESHOLD_MILLIS);
     duration_of_next_frame_ =
         std::max(std::min(duration_of_next_frame_, upper_bound),
                  smoothing_sampler_.min_capture_period());
@@ -337,24 +340,6 @@
   estimated_capable_area_.Update(area_at_full_utilization, timestamp);
 }
 
-// static
-const char* VideoCaptureOracle::EventAsString(Event event) {
-  switch (event) {
-    case kCompositorUpdate:
-      return "compositor";
-    case kActiveRefreshRequest:
-      return "active_refresh";
-    case kPassiveRefreshRequest:
-      return "passive_refresh";
-    case kMouseCursorUpdate:
-      return "mouse";
-    case kNumEvents:
-      break;
-  }
-  NOTREACHED();
-  return "unknown";
-}
-
 base::TimeTicks VideoCaptureOracle::GetFrameTimestamp(int frame_number) const {
   DCHECK(IsFrameInRecentHistory(frame_number));
   return frame_timestamps_[frame_number % kMaxFrameTimestamps];