Introduce DecodeTimestamp class to make it easier to distiguish presentation and decode timestamps.

media/base/stream_parser.cc

Index: media/base/stream_parser.cc
diff --git a/media/base/stream_parser.cc b/media/base/stream_parser.cc
index 59c3ed60796c83e13b9c763e540d4d4526d98baa..942afbf8ec93a9df3f660c987a11c2ab10da8769 100644
--- a/media/base/stream_parser.cc
+++ b/media/base/stream_parser.cc
@@ -48,7 +48,7 @@ static bool MergeBufferQueuesInternal(
   // buffers must not be less than. If |merged_buffers| already has buffers,
   // initialize |last_decode_timestamp| to the decode timestamp of the last
   // buffer in it.
-  base::TimeDelta last_decode_timestamp = kNoTimestamp();
+  DecodeTimestamp last_decode_timestamp = kNoDecodeTimestamp();
   if (!merged_buffers->empty())
     last_decode_timestamp = merged_buffers->back()->GetDecodeTimestamp();
 
@@ -70,7 +70,7 @@ static bool MergeBufferQueuesInternal(
     // Tracks which queue's iterator is pointing to the candidate buffer to
     // append next, or -1 if no candidate buffers found. This indexes |itrs|.
     int index_of_queue_with_next_decode_timestamp = -1;
-    base::TimeDelta next_decode_timestamp = kNoTimestamp();
+    DecodeTimestamp next_decode_timestamp = kNoDecodeTimestamp();
 
     // Scan each of the iterators for |buffer_queues| to find the candidate
     // buffer, if any, that has the lowest decode timestamp.
@@ -79,14 +79,14 @@ static bool MergeBufferQueuesInternal(
         continue;
 
       // Extract the candidate buffer's decode timestamp.
-      base::TimeDelta ts = (*itrs[i])->GetDecodeTimestamp();
+      DecodeTimestamp ts = (*itrs[i])->GetDecodeTimestamp();
 
-      if (last_decode_timestamp != kNoTimestamp() &&
+      if (last_decode_timestamp != kNoDecodeTimestamp() &&
           ts < last_decode_timestamp)
         return false;
 
       if (ts < next_decode_timestamp ||
-          next_decode_timestamp == kNoTimestamp()) {
+          next_decode_timestamp == kNoDecodeTimestamp()) {
         // Remember the decode timestamp and queue iterator index for this
         // potentially winning candidate buffer.
         next_decode_timestamp = ts;