audio: Remove unused field Panner::panning_model_.

Change-Id: I53d62db14db0ff6908726c9fc9e61492f9cb1276
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2561751
Auto-Submit: Jeremy Roman <jbroman@chromium.org>
Reviewed-by: Raymond Toy <rtoy@chromium.org>
Commit-Queue: Raymond Toy <rtoy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#831899}

third_party/blink/renderer/platform/audio/equal_power_panner.cc

@@ -33,8 +33,7 @@
 
 namespace blink {
 
-EqualPowerPanner::EqualPowerPanner(float sample_rate)
-    : Panner(PanningModel::kEqualPower) {}
+EqualPowerPanner::EqualPowerPanner(float sample_rate) {}
 
 void EqualPowerPanner::Pan(double azimuth,
                            double /*elevation*/,

third_party/blink/renderer/platform/audio/hrtf_panner.cc

@@ -42,8 +42,7 @@ const double kMaxDelayTimeSeconds = 0.002;
 const int kUninitializedAzimuth = -1;
 
 HRTFPanner::HRTFPanner(float sample_rate, HRTFDatabaseLoader* database_loader)
-    : Panner(PanningModel::kHRTF),
-      database_loader_(database_loader),
+    : database_loader_(database_loader),
       sample_rate_(sample_rate),
       crossfade_selection_(kCrossfadeSelection1),
       azimuth_index1_(kUninitializedAzimuth),

third_party/blink/renderer/platform/audio/panner.h

@@ -80,9 +80,7 @@ class PLATFORM_EXPORT Panner {
   virtual bool RequiresTailProcessing() const = 0;
 
  protected:
-  explicit Panner(PanningModel model) : panning_model_(model) {}
-
-  PanningModel panning_model_;
+  Panner() = default;
 
  private:
   DISALLOW_COPY_AND_ASSIGN(Panner);