Move usage of QualityScaler to ViEEncoder.

webrtc/video_encoder.h

Index: webrtc/video_encoder.h
diff --git a/webrtc/video_encoder.h b/webrtc/video_encoder.h
index 9bfec55eb7ddc48659b0063ebc13fa3c4f49c7bb..4030c513fe51910296066386fad898b43576848e 100644
--- a/webrtc/video_encoder.h
+++ b/webrtc/video_encoder.h
@@ -18,6 +18,7 @@
 #include "webrtc/common_types.h"
 #include "webrtc/typedefs.h"
 #include "webrtc/video_frame.h"
+#include "webrtc/base/optional.h"
 
 namespace webrtc {
 
@@ -81,6 +82,7 @@ class VideoEncoder {
     kVp9,
     kUnsupportedCodec,
   };
+  typedef std::pair<int, int> QPThresholds;
 
   static VideoEncoder* Create(EncoderType codec_type);
 
@@ -159,6 +161,12 @@ class VideoEncoder {
   // Return value                : WEBRTC_VIDEO_CODEC_OK if OK, < 0 otherwise.
   virtual int32_t SetRates(uint32_t bitrate, uint32_t framerate) = 0;
 
+  // If a specific set of thresholds are desired for quality scaling
+  // an encoder implementation can override this method.
+  virtual rtc::Optional<QPThresholds> GetQPThresholds() {
+    return rtc::Optional<QPThresholds>();
+  }
+
   virtual int32_t SetPeriodicKeyFrames(bool enable) { return -1; }
   virtual void OnDroppedFrame() {}
   virtual bool SupportsNativeHandle() const { return false; }