GTTF: Enable glibcxx debug mode for Debug builds by default.

media/filters/source_buffer_stream.cc

Index: media/filters/source_buffer_stream.cc
diff --git a/media/filters/source_buffer_stream.cc b/media/filters/source_buffer_stream.cc
index 03de160b557314c2a27949745233728292dcc47c..5fada5c5508fe075efbdf89149e0a9056e7d627f 100644
--- a/media/filters/source_buffer_stream.cc
+++ b/media/filters/source_buffer_stream.cc
@@ -381,7 +381,6 @@ void SourceBufferStream::OnNewMediaSegment(
   media_segment_start_time_ = media_segment_start_time;
   new_media_segment_ = true;
 
-  RangeList::iterator last_range = range_for_next_append_;
   range_for_next_append_ = FindExistingRangeFor(media_segment_start_time);
 
   // Only reset |last_appended_buffer_timestamp_| if this new media segment is
@@ -391,8 +390,6 @@ void SourceBufferStream::OnNewMediaSegment(
                              media_segment_start_time)) {
     last_appended_buffer_timestamp_ = kNoTimestamp();
     last_appended_buffer_is_keyframe_ = false;
-  } else {
-    DCHECK(last_range == range_for_next_append_);
   }
 }