Revert of Remove VCMQmRobustness. (patchset #1 id:1 of https://codereview.webrtc.org/1917083003/ )

Reason for revert:
Speculative revert for perf regression.

Original issue's description:
> Remove VCMQmRobustness.
>
> Class contained a lot of not-really-wired-up functionality that ended up
> being complicated ways of saying return 1; or return false;. This
> removes this dependency that complicates code readability significantly.
>
> BUG=webrtc:5066
> R=marpan@google.com, marpan@webrtc.org
> TBR=stefan@webrtc.org
>
> Committed: https://crrev.com/73894369791cb5eedc8788baf918ec07d11d351d
> Cr-Commit-Position: refs/heads/master@{#12516}

TBR=marpan@webrtc.org,stefan@webrtc.org,marpan@google.com
# Not skipping CQ checks because original CL landed more than 1 days ago.
BUG=webrtc:5066, chromium:607838

Review-Url: https://codereview.webrtc.org/1935753002
Cr-Commit-Position: refs/heads/master@{#12572}

webrtc/modules/video_coding/qm_select.cc

@@ -898,4 +898,56 @@ void VCMQmResolution::SelectSpatialDirectionMode(float transition_rate) {
   }
 }
 
+// ROBUSTNESS CLASS
+
+VCMQmRobustness::VCMQmRobustness() {
+  Reset();
+}
+
+VCMQmRobustness::~VCMQmRobustness() {}
+
+void VCMQmRobustness::Reset() {
+  prev_total_rate_ = 0.0f;
+  prev_rtt_time_ = 0;
+  prev_packet_loss_ = 0;
+  prev_code_rate_delta_ = 0;
+  ResetQM();
+}
+
+// Adjust the FEC rate based on the content and the network state
+// (packet loss rate, total rate/bandwidth, round trip time).
+// Note that packetLoss here is the filtered loss value.
+float VCMQmRobustness::AdjustFecFactor(uint8_t code_rate_delta,
+                                       float total_rate,
+                                       float framerate,
+                                       int64_t rtt_time,
+                                       uint8_t packet_loss) {
+  // Default: no adjustment
+  float adjust_fec = 1.0f;
+  if (content_metrics_ == NULL) {
+    return adjust_fec;
+  }
+  // Compute class state of the content.
+  ComputeMotionNFD();
+  ComputeSpatial();
+
+  // TODO(marpan): Set FEC adjustment factor.
+
+  // Keep track of previous values of network state:
+  // adjustment may be also based on pattern of changes in network state.
+  prev_total_rate_ = total_rate;
+  prev_rtt_time_ = rtt_time;
+  prev_packet_loss_ = packet_loss;
+  prev_code_rate_delta_ = code_rate_delta;
+  return adjust_fec;
+}
+
+// Set the UEP (unequal-protection across packets) on/off for the FEC.
+bool VCMQmRobustness::SetUepProtection(uint8_t code_rate_delta,
+                                       float total_rate,
+                                       uint8_t packet_loss,
+                                       bool frame_type) {
+  // Default.
+  return false;
+}
 }  // namespace webrtc