Revert of Properly report number of quality downscales in stats. (patchset #11 id:220001 of https://codereview.webrtc.org/2564373002/ )

Reason for revert:
Breaks perf tests

Original issue's description:
> Properly report number of quality downscales in stats.
>
> A regression was introduced in 876222f that caused these stats to
> be reported incorrectly. This used to be only implemented for VP8
> but should now be available for all codecs.
>
> BUG=webrtc:6860
>
> Review-Url: https://codereview.webrtc.org/2564373002
> Cr-Commit-Position: refs/heads/master@{#15673}
> Committed: https://chromium.googlesource.com/external/webrtc/+/0c8c5388355f5df085595d9ea24fa38995708120

TBR=asapersson@webrtc.org,stefan@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:6860

Review-Url: https://codereview.webrtc.org/2586783003
Cr-Commit-Position: refs/heads/master@{#15678}
diff --git a/webrtc/video_frame.h b/webrtc/video_frame.h
index bec43f8..5fd62a6 100644
--- a/webrtc/video_frame.h
+++ b/webrtc/video_frame.h
@@ -136,10 +136,14 @@
   EncodedImage(uint8_t* buffer, size_t length, size_t size)
       : _buffer(buffer), _length(length), _size(size) {}
 
-  // TODO(kthelgason): get rid of this struct as it only has a single member
-  // remaining.
   struct AdaptReason {
-    AdaptReason() : bw_resolutions_disabled(-1) {}
+    AdaptReason()
+        : quality_resolution_downscales(-1),
+          bw_resolutions_disabled(-1) {}
+
+    int quality_resolution_downscales;  // Number of times this frame is down
+                                        // scaled in resolution due to quality.
+                                        // Or -1 if information is not provided.
     int bw_resolutions_disabled;  // Number of resolutions that are not sent
                                   // due to bandwidth for this frame.
                                   // Or -1 if information is not provided.