Revert of Multibuffer reader implementation

media/blink/interval_map.h

 // Copyright 2015 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.
 
 #ifndef MEDIA_BLINK_INTERVAL_MAP_H_
 #define MEDIA_BLINK_INTERVAL_MAP_H_
 
 #include <limits>
 #include <map>
 
@@ skipping 106 matching lines @@
   }
 
   // Returns the value associated with the current interval.
   ValueType value() const {
     DCHECK(iter_ != map_->end());
     return iter_->second;
   }
 
   // Needed to make the following construct work:
   // for (const auto& interval_value_pair : interval_map)
+  // Note however that this will skip the "end" interval, which
+  // is usually ok since it generally has the default value.
   std::pair<Interval<KeyType>, ValueType> operator*() const {
     return std::make_pair(interval(), value());
   }
 
   // Go to the next interval.
   // The beginning of the next interval always matches the end of the current
   // interval. (But should always have a different value.)
   // Not allowed if we're already at map_->end().
   void operator++() {
     DCHECK(iter_ != map_->end());
@@ skipping 36 matching lines @@
   // Defaults to ValueType().
   ValueType operator[](const KeyType& k) const {
     typename MapType::const_iterator i = map_.upper_bound(k);
     DCHECK(i != map_.begin());
     --i;
     return i->second;
   }
 
   // Increase [from..to) by |how_much|.
   void IncrementInterval(KeyType from, KeyType to, ValueType how_much) {
-    if (to <= from || how_much == 0)
+    DCHECK_GT(to, from);
+    if (how_much == 0)
       return;
     typename MapType::iterator a = MakeEntry(from);
     typename MapType::iterator b = MakeEntry(to);
     for (typename MapType::iterator i = a; i != b; ++i) {
       i->second += how_much;
     }
     RemoveDuplicates(a);
     // b may be invalid
     RemoveDuplicates(map_.lower_bound(to));
   }
 
   // Set [from..to) to |how_much|.
   void SetInterval(KeyType from, KeyType to, ValueType how_much) {
-    if (to <= from)
-      return;
+    DCHECK_GT(to, from);
     typename MapType::iterator a = MakeEntry(from);
     typename MapType::iterator b = MakeEntry(to);
     a->second = how_much;
     while (true) {
       typename MapType::iterator c = a;
       ++c;
       if (c == b) {
         break;
       } else {
         map_.erase(c);
@@ skipping 70 matching lines @@
       map_.erase(second);
     }
   }
 
   MapType map_;
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BLINK_INTERVAL_MAP_H_