Fix crashes caused when SourceBuffer.remove() is called starting at the presentation duration.

media/filters/chunk_demuxer.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 "media/filters/chunk_demuxer.h"
 
 #include <algorithm>
 #include <limits>
 #include <list>
 
@@ skipping 1304 matching lines @@
 }
 
 void ChunkDemuxer::Remove(const std::string& id, TimeDelta start,
                           TimeDelta end) {
   DVLOG(1) << "Remove(" << id << ", " << start.InSecondsF()
            << ", " << end.InSecondsF() << ")";
   base::AutoLock auto_lock(lock_);
 
   DCHECK(!id.empty());
   CHECK(IsValidId(id));
+  DCHECK(start >= base::TimeDelta()) << start.InSecondsF();
+  DCHECK(start < end) << "start " << start.InSecondsF()
+                      << " end " << end.InSecondsF();
+  DCHECK(duration_ != kNoTimestamp());
+  DCHECK(start <= duration_) << "start " << start.InSecondsF()
+                             << " duration " << duration_.InSecondsF();
+
+  if (start == duration_)
+    return;
+
   source_state_map_[id]->Remove(start, end, duration_);
 }
 
 double ChunkDemuxer::GetDuration() {
   base::AutoLock auto_lock(lock_);
   return GetDuration_Locked();
 }
 
 double ChunkDemuxer::GetDuration_Locked() {
   lock_.AssertAcquired();
@@ skipping 399 matching lines @@
 }
 
 void ChunkDemuxer::ShutdownAllStreams() {
   for (SourceStateMap::iterator itr = source_state_map_.begin();
        itr != source_state_map_.end(); ++itr) {
     itr->second->Shutdown();
   }
 }
 
 }  // namespace media