Remove candidates when doing continual gathering

talk/app/webrtc/jsepsessiondescription.cc

Index: talk/app/webrtc/jsepsessiondescription.cc
diff --git a/talk/app/webrtc/jsepsessiondescription.cc b/talk/app/webrtc/jsepsessiondescription.cc
index 226432db6956d63852d536fcb40fc68c778a8ec4..1ddbbba37af205795973d4a293c01addf6d89614 100644
--- a/talk/app/webrtc/jsepsessiondescription.cc
+++ b/talk/app/webrtc/jsepsessiondescription.cc
@@ -154,6 +154,22 @@ bool JsepSessionDescription::AddCandidate(
   return true;
 }
 
+bool JsepSessionDescription::RemoveCandidate(
+    const IceCandidateInterface* candidate) {
+  if (!candidate || candidate->sdp_mline_index() < 0 ||
+      candidate->candidate().priority() != 0) {
+    return false;
+  }
+  size_t mediasection_index = 0;
+  if (!GetMediasectionIndex(candidate, &mediasection_index) ||
+      mediasection_index >= number_of_mediasections()) {
+    return false;
+  }
+  int num_removed = candidate_collection_[mediasection_index].remove(candidate);
+  ASSERT(num_removed <= 1);
+  return num_removed > 0;
+}
+
 size_t JsepSessionDescription::number_of_mediasections() const {
   if (!description_)
     return 0;