Make rtc::TimestampWrapAroundHandler handle backwards wrapping

webrtc/base/timeutils.cc

Index: webrtc/base/timeutils.cc
diff --git a/webrtc/base/timeutils.cc b/webrtc/base/timeutils.cc
index 24b04ee2ee46342c1551901309042f8f4438955a..0d7273299efdd213498540faedb9f00d1b81cd9c 100644
--- a/webrtc/base/timeutils.cc
+++ b/webrtc/base/timeutils.cc
@@ -200,10 +200,12 @@ int64_t TimestampWrapAroundHandler::Unwrap(uint32_t ts) {
     if (last_ts_ > 0xf0000000 && ts < 0x0fffffff) {
       ++num_wrap_;
     }
+  } else if (num_wrap_ > 0 && (ts - last_ts_) >= 0x0fffffff) {
+    // Backwards wrap. Unwrap with last wrap count and don't update last_ts_.
+    return ts + ((num_wrap_ -1) << 32);

[mflodman, 2016/03/09 15:01:57]

Functionality LG, but can this be written in an easy way to still only have one
return for this method?

To have better readability and logic.

[sprang_webrtc, 2016/03/09 15:40:30]

Not without duplicating "last_ts = ts" or adding an ugly temporary for num_wrap
I agree it's a little hard to follow, but the alternatives are pretty messy too.
Otherwise I could rewrite it entirely in a more verbose way.

   }
   last_ts_ = ts;
-  int64_t unwrapped_ts = ts + (num_wrap_ << 32);
-  return unwrapped_ts;
+  return ts + (num_wrap_ << 32);
 }
 
 int64_t TmToSeconds(const std::tm& tm) {