Add stats for average QP per frame for VP8 (for received video streams):

"WebRTC.Video.Decoded.VP8.Qp"

BUG=chromium:512752

Review URL: https://codereview.webrtc.org/1340623002

Cr-Commit-Position: refs/heads/master@{#10349}

webrtc/modules/video_coding/utility/include/qp_parser.h

@@ -0,0 +1,30 @@
+/*
+ *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef WEBRTC_MODULES_VIDEO_CODING_UTILITY_QP_PARSER_H_
+#define WEBRTC_MODULES_VIDEO_CODING_UTILITY_QP_PARSER_H_
+
+#include "webrtc/modules/video_coding/main/source/encoded_frame.h"
+
+namespace webrtc {
+
+class QpParser {
+ public:
+  QpParser() {}
+  ~QpParser() {}
+
+  // Parses an encoded |frame| and extracts the |qp|.
+  // Returns true on success, false otherwise.
+  bool GetQp(const VCMEncodedFrame& frame, int* qp);
+};
+
+}  // namespace webrtc
+
+#endif  // WEBRTC_MODULES_VIDEO_CODING_UTILITY_QP_PARSER_H_