Add vp9 QP parser.

BUG=webrtc:7662

Review-Url: https://codereview.webrtc.org/2891803003
Cr-Commit-Position: refs/heads/master@{#18260}
diff --git a/webrtc/modules/video_coding/qp_parser.cc b/webrtc/modules/video_coding/qp_parser.cc
index 976cfff..26b46f1 100644
--- a/webrtc/modules/video_coding/qp_parser.cc
+++ b/webrtc/modules/video_coding/qp_parser.cc
@@ -12,6 +12,7 @@
 
 #include "webrtc/common_types.h"
 #include "webrtc/modules/video_coding/utility/vp8_header_parser.h"
+#include "webrtc/modules/video_coding/utility/vp9_uncompressed_header_parser.h"
 
 namespace webrtc {
 
@@ -20,6 +21,9 @@
     case kVideoCodecVP8:
       // QP range: [0, 127].
       return vp8::GetQp(frame.Buffer(), frame.Length(), qp);
+    case kVideoCodecVP9:
+      // QP range: [0, 255].
+      return vp9::GetQp(frame.Buffer(), frame.Length(), qp);
     default:
       return false;
   }