Revert of Multibuffer reader implementation

media/blink/interval_map.h

Index: media/blink/interval_map.h
diff --git a/media/blink/interval_map.h b/media/blink/interval_map.h
index 74cdca71cf2dbf8c71309b3ccc1a0ca8fd9c2355..e11a03ceef7abbba90dc105f6dcce49ca1da212e 100644
--- a/media/blink/interval_map.h
+++ b/media/blink/interval_map.h
@@ -124,6 +124,8 @@
 
   // 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());
   }
@@ -180,7 +182,8 @@
 
   // 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);
@@ -194,8 +197,7 @@
 
   // 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;