TabCapture: enforce active refresh if there is un-sampled compositor update

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 b1dcb80adeef3bd307a352afd04843d9f80b5ac5..ada05ff558ca01fff63da9c6e5947c18237ee3b3 100644
--- a/media/capture/content/video_capture_oracle.cc
+++ b/media/capture/content/video_capture_oracle.cc
@@ -101,6 +101,8 @@ VideoCaptureOracle::VideoCaptureOracle(
     bool enable_auto_throttling)
     : auto_throttling_enabled_(enable_auto_throttling),
       next_frame_number_(0),
+      source_is_dirty_(true),
+      last_event_causing_capture_(kPassiveRefreshRequest),
       last_successfully_delivered_frame_number_(-1),
       num_frames_pending_(0),
       smoothing_sampler_(min_capture_period),
@@ -138,6 +140,11 @@ bool VideoCaptureOracle::ObserveEventAndDecideCapture(
   }
   last_event_time_[event] = event_time;
 
+  // If the event indicates a change to the source content, set a flag that will
+  // prevent passive refresh requests until a capture is made.
+  if (event != kActiveRefreshRequest && event != kPassiveRefreshRequest)
+    source_is_dirty_ = true;
+
   bool should_sample = false;
   duration_of_next_frame_ = base::TimeDelta();
   switch (event) {
@@ -160,8 +167,11 @@ bool VideoCaptureOracle::ObserveEventAndDecideCapture(
       break;
     }
 
-    case kActiveRefreshRequest:
     case kPassiveRefreshRequest:
+      if (source_is_dirty_)
+        break;
+    // Intentional flow-through to next case here!
+    case kActiveRefreshRequest:
     case kMouseCursorUpdate:
       // Only allow non-compositor samplings when content has not recently been
       // animating, and only if there are no samplings currently in progress.
@@ -182,6 +192,7 @@ bool VideoCaptureOracle::ObserveEventAndDecideCapture(
 
   if (!should_sample)
     return false;
+  last_event_causing_capture_ = event;
 
   // If the exact duration of the next frame has not been determined, estimate
   // it using the difference between the current and last frame.
@@ -221,6 +232,9 @@ int VideoCaptureOracle::next_frame_number() const {
 void VideoCaptureOracle::RecordCapture(double pool_utilization) {
   DCHECK(std::isfinite(pool_utilization) && pool_utilization >= 0.0);
 
+  if (last_event_causing_capture_ != kPassiveRefreshRequest)

[miu, 2017/03/24 21:17:28]

Per discussion, this shouldn't be necessary. So, just:

  source_is_dirty_ = false;

[braveyao, 2017/03/24 23:12:27]

Done.

+    source_is_dirty_ = false;
+
   smoothing_sampler_.RecordSample();
   const base::TimeTicks timestamp = GetFrameTimestamp(next_frame_number_);
   content_sampler_.RecordSample(timestamp);
@@ -271,6 +285,9 @@ bool VideoCaptureOracle::CompleteCapture(int frame_number,
 
   if (!capture_was_successful) {
     VLOG(2) << "Capture of frame #" << frame_number << " was not successful.";
+    // Since capture of this frame might have been required for capturing an
+    // update to the source content, set the dirty flag.
+    source_is_dirty_ = true;
     return false;
   }