Reland the CL to remove candidates when doing continual gathering

webrtc/api/jsepsessiondescription.cc

 /*
  *  Copyright 2012 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 119 matching lines @@
                            static_cast<int>(mediasection_index),
                            updated_candidate));
   if (!candidate_collection_[mediasection_index].HasCandidate(
           updated_candidate_wrapper.get()))
     candidate_collection_[mediasection_index].add(
         updated_candidate_wrapper.release());
 
   return true;
 }
 
+size_t JsepSessionDescription::RemoveCandidates(
+    const std::vector<cricket::Candidate>& candidates) {
+  size_t num_removed = 0;
+  for (auto& candidate : candidates) {
+    int mediasection_index = GetMediasectionIndex(candidate);
+    if (mediasection_index < 0) {
+      // Not found.
+      continue;
+    }
+    num_removed += candidate_collection_[mediasection_index].remove(candidate);
+  }
+  return num_removed;
+}
+
 size_t JsepSessionDescription::number_of_mediasections() const {
   if (!description_)
     return 0;
   return description_->contents().size();
 }
 
 const IceCandidateCollection* JsepSessionDescription::candidates(
     size_t mediasection_index) const {
   if (mediasection_index >= candidate_collection_.size())
     return NULL;
@@ skipping 27 matching lines @@
     }
     if (!found) {
       // If the sdp_mid is presented but we can't find a match, we consider
       // this as an error.
       return false;
     }
   }
   return true;
 }
 
+int JsepSessionDescription::GetMediasectionIndex(
+    const cricket::Candidate& candidate) {
+  // Find the description with a matching transport name of the candidate.
+  const std::string& transport_name = candidate.transport_name();
+  for (size_t i = 0; i < description_->contents().size(); ++i) {
+    if (transport_name == description_->contents().at(i).name) {
+      return static_cast<int>(i);
+    }
+  }
+  return -1;
+}
+
 }  // namespace webrtc