Remove empty-string comparisons.

talk/app/webrtc/webrtcsdp.cc

 /*
  * libjingle
  * Copyright 2011 Google Inc.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are met:
  *
  *  1. Redistributions of source code must retain the above copyright notice,
  *     this list of conditions and the following disclaimer.
  *  2. Redistributions in binary form must reproduce the above copyright notice,
@@ skipping 2174 matching lines @@
     }
 
     std::string protocol = fields[2];
 
     // <fmt>
     std::vector<int> codec_preference;
     if (IsRtp(protocol)) {
       for (size_t j = 3 ; j < fields.size(); ++j) {
         // TODO(wu): Remove when below bug is fixed.
         // https://bugzilla.mozilla.org/show_bug.cgi?id=996329
-        if (fields[j] == "" && j == fields.size() - 1) {
+        if (fields[j].empty() && j == fields.size() - 1) {
           continue;
         }
 
         int pl = 0;
         if (!GetPayloadTypeFromString(line, fields[j], &pl, error)) {
           return false;
         }
         codec_preference.push_back(pl);
       }
     }
@@ skipping 892 matching lines @@
     UpdateCodec<AudioContentDescription, cricket::AudioCodec>(
         media_desc, payload_type, feedback_param);
   } else if (media_type == cricket::MEDIA_TYPE_VIDEO) {
     UpdateCodec<VideoContentDescription, cricket::VideoCodec>(
         media_desc, payload_type, feedback_param);
   }
   return true;
 }
 
 }  // namespace webrtc