multibuffer: Evict lower blocks first after inserting multiple blocks

media/blink/multibuffer.cc

Index: media/blink/multibuffer.cc
diff --git a/media/blink/multibuffer.cc b/media/blink/multibuffer.cc
index c17d80c81aa6eef5565d7ed04b201792935c7407..a59ac5e854232277ecbaf4c153ed0413fd0159d9 100644
--- a/media/blink/multibuffer.cc
+++ b/media/blink/multibuffer.cc
@@ -460,8 +460,6 @@ void MultiBuffer::PinRange(const BlockId& from,
   // Iterate over all the modified ranges and check if any of them have
   // transitioned in or out of the unlocked state. If so, we iterate over
   // all buffers in that range and add/remove them from the LRU as approperiate.
-  // We iterate *backwards* through the ranges, with the idea that data in a
-  // continous range should be freed from the end first.
 
   if (data_.empty())
     return;
@@ -479,16 +477,16 @@ void MultiBuffer::PinRange(const BlockId& from,
       // For each range that has transitioned to/from a pinned state,
       // we iterate over the corresponding ranges in |present_| to find
       // the blocks that are actually in the multibuffer.
-      for (auto present_block_range = present_.find(transition_range.end - 1);
-           present_block_range != present_.begin(); --present_block_range) {
+      for (auto present_block_range = present_.find(transition_range.begin);
+           present_block_range != present_.end(); ++present_block_range) {
         if (!present_block_range.value())
           continue;
         Interval<BlockId> present_transitioned_range =
             transition_range.Intersect(present_block_range.interval());
         if (present_transitioned_range.Empty())
           break;
-        for (BlockId block = present_transitioned_range.end - 1;
-             block >= present_transitioned_range.begin; --block) {
+        for (BlockId block = present_transitioned_range.begin;
+             block < present_transitioned_range.end; ++block) {
           DCHECK_GE(block, 0);
           DCHECK(data_.find(block) != data_.end());
           if (pin) {