Add a couple of checks to FrameBuffer while we're continuing to look at RtpFrameReferenceFinder.

webrtc/modules/video_coding/frame_buffer2.cc

 /*
  *  Copyright (c) 2016 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
@@ skipping 300 matching lines @@
       if (frame_ref->second.num_missing_continuous == 0) {
         frame_ref->second.continuous = true;
         continuous_frames.push(frame_ref);
       }
     }
   }
 }
 
 void FrameBuffer::PropagateDecodability(const FrameInfo& info) {
   TRACE_EVENT0("webrtc", "FrameBuffer::PropagateDecodability");
+  RTC_CHECK(info.num_dependent_frames < FrameInfo::kMaxNumDependentFrames);
   for (size_t d = 0; d < info.num_dependent_frames; ++d) {
     auto ref_info = frames_.find(info.dependent_frames[d]);
     RTC_DCHECK(ref_info != frames_.end());
-    RTC_DCHECK_GT(ref_info->second.num_missing_decodable, 0U);
-    --ref_info->second.num_missing_decodable;
+    // TODO(philipel): Look into why we've seen this happen.
+    if (ref_info != frames_.end()) {
+      RTC_DCHECK_GT(ref_info->second.num_missing_decodable, 0U);
+      --ref_info->second.num_missing_decodable;
+    }
   }
 }
 
 void FrameBuffer::AdvanceLastDecodedFrame(FrameMap::iterator decoded) {
   TRACE_EVENT0("webrtc", "FrameBuffer::AdvanceLastDecodedFrame");
   if (last_decoded_frame_it_ == frames_.end()) {
     last_decoded_frame_it_ = frames_.begin();
   } else {
     RTC_DCHECK(last_decoded_frame_it_->first < decoded->first);
     ++last_decoded_frame_it_;
@@ skipping 48 matching lines @@
       if (ref_info == frames_.end())
         ref_info = frames_.insert(std::make_pair(ref_key, FrameInfo())).first;
 
       if (ref_info->second.continuous)
         --info->second.num_missing_continuous;
 
       // Add backwards reference so |frame| can be updated when new
       // frames are inserted or decoded.
       ref_info->second.dependent_frames[ref_info->second.num_dependent_frames] =
           key;
-      ++ref_info->second.num_dependent_frames;
+      RTC_DCHECK_LT(ref_info->second.num_dependent_frames,
+                    (FrameInfo::kMaxNumDependentFrames - 1));
+      // TODO(philipel): Look into why this could happen and handle
+      // appropriately.
+      if (ref_info->second.num_dependent_frames <
+          (FrameInfo::kMaxNumDependentFrames - 1)) {
+        ++ref_info->second.num_dependent_frames;
+      }
     }
     RTC_DCHECK_LE(ref_info->second.num_missing_continuous,
                   ref_info->second.num_missing_decodable);
   }
 
   // Check if we have the lower spatial layer frame.
   if (frame.inter_layer_predicted) {
     ++info->second.num_missing_continuous;
     ++info->second.num_missing_decodable;
 
@@ skipping 46 matching lines @@
   frames_.clear();
   last_decoded_frame_it_ = frames_.end();
   last_continuous_frame_it_ = frames_.end();
   next_frame_it_ = frames_.end();
   num_frames_history_ = 0;
   num_frames_buffered_ = 0;
 }
 
 }  // namespace video_coding
 }  // namespace webrtc