Removed invalid thread DCHECKs in rtc_peer_connection_handler.cc

content/renderer/media/rtc_peer_connection_handler.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/renderer/media/rtc_peer_connection_handler.h"
 
 #include <string.h>
 
 #include <string>
 #include <utility>
@@ skipping 374 matching lines @@
       return;
     }
 
     tracker_.TrackOnFailure(error);
     webkit_request_.requestFailed(base::UTF8ToUTF16(error));
     webkit_request_.reset();
   }
 
  protected:
   ~CreateSessionDescriptionRequest() override {
-    DCHECK(main_thread_->BelongsToCurrentThread());
+    // This object is reference counted and its callback methods |OnSuccess| and
+    // |OnFailure| may be invoked on any thread, for non-main threads the

[perkj_chrome, 2016/08/17 11:16:14]

I had problem reading the sentence  
"This object is reference counted and its callback methods |OnSuccess| and
 |OnFailure| may be invoked on any thread, for non-main threads the ...."

May I suggest something like  // |OnFailure| will be invoked on libjingles
signaling thread and posted to the main thread. Since the main thread may
complete before the signaling thread has deferenced this object there is no
guarante.... 

[hbos_chromium, 2016/08/17 13:53:26]

Done.

+    // callback is posted to the main thread. Since the post may complete before
+    // the non-main thread has dereferenced this object there is no guarantee
+    // that this object is destructed on the main thread.
     DLOG_IF(ERROR, !webkit_request_.isNull())
         << "CreateSessionDescriptionRequest not completed. Shutting down?";
   }
 
   const scoped_refptr<base::SingleThreadTaskRunner> main_thread_;
   blink::WebRTCSessionDescriptionRequest webkit_request_;
   SessionDescriptionRequestTracker tracker_;
 };
 
 // Class mapping responses from calls to libjingle
@@ skipping 28 matching lines @@
           base::Bind(&SetSessionDescriptionRequest::OnFailure, this, error));
       return;
     }
     tracker_.TrackOnFailure(error);
     webkit_request_.requestFailed(base::UTF8ToUTF16(error));
     webkit_request_.reset();
   }
 
  protected:
   ~SetSessionDescriptionRequest() override {
-    DCHECK(main_thread_->BelongsToCurrentThread());
+    // This object is reference counted and its callback methods |OnSuccess| and
+    // |OnFailure| may be invoked on any thread, for non-main threads the
+    // callback is posted to the main thread. Since the post may complete before
+    // the non-main thread has dereferenced this object there is no guarantee
+    // that this object is destructed on the main thread.
     DLOG_IF(ERROR, !webkit_request_.isNull())
         << "SetSessionDescriptionRequest not completed. Shutting down?";
   }
 
  private:
   const scoped_refptr<base::SingleThreadTaskRunner> main_thread_;
   blink::WebRTCVoidRequest webkit_request_;
   SessionDescriptionRequestTracker tracker_;
 };
 
@@ skipping 1439 matching lines @@
 }
 
 void RTCPeerConnectionHandler::ResetUMAStats() {
   DCHECK(thread_checker_.CalledOnValidThread());
   num_local_candidates_ipv6_ = 0;
   num_local_candidates_ipv4_ = 0;
   ice_connection_checking_start_ = base::TimeTicks();
   memset(ice_state_seen_, 0, sizeof(ice_state_seen_));
 }
 }  // namespace content