Adding method IsInBeam to beamformer class.

This was previously reviewed at:
https://webrtc-codereview.appspot.com/53729004/

Review URL: https://codereview.webrtc.org/1211613005

Cr-Commit-Position: refs/heads/master@{#9517}

webrtc/modules/audio_processing/beamformer/beamformer.h

@@ -31,6 +31,9 @@ class Beamformer {
   // Needs to be called before the the Beamformer can be used.
   virtual void Initialize(int chunk_size_ms, int sample_rate_hz) = 0;
 
+  // Indicates whether a given point is inside of the beam.
+  virtual bool IsInBeam(const SphericalPointf& spherical_point) { return true; }
+
   // Returns true if the current data contains the target signal.
   // Which signals are considered "targets" is implementation dependent.
   virtual bool is_target_present() = 0;

webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.cc

@@ -50,6 +50,8 @@ const float kInterfAngleRadians = static_cast<float>(M_PI) / 4.f;
 // Rpsi = Rpsi_angled * kBalance + Rpsi_uniform * (1 - kBalance)
 const float kBalance = 0.4f;
 
+const float kHalfBeamWidthRadians = static_cast<float>(M_PI) * 20.f / 180.f;
+
 // TODO(claguna): need comment here.
 const float kBeamwidthConstant = 0.00002f;
 
@@ -334,6 +336,13 @@ void NonlinearBeamformer::ProcessChunk(const ChannelBuffer<float>& input,
   }
 }
 
+bool NonlinearBeamformer::IsInBeam(const SphericalPointf& spherical_point) {
+  // If more than half-beamwidth degrees away from the beam's center,
+  // you are out of the beam.
+  return fabs(spherical_point.azimuth() - kTargetAngleRadians) <
+         kHalfBeamWidthRadians;
+}
+
 void NonlinearBeamformer::ProcessAudioBlock(const complex_f* const* input,
                                             int num_input_channels,
                                             int num_freq_bins,

webrtc/modules/audio_processing/beamformer/nonlinear_beamformer.h

@@ -48,6 +48,8 @@ class NonlinearBeamformer
   void ProcessChunk(const ChannelBuffer<float>& input,
                     ChannelBuffer<float>* output) override;
 
+  bool IsInBeam(const SphericalPointf& spherical_point) override;
+
   // After processing each block |is_target_present_| is set to true if the
   // target signal es present and to false otherwise. This methods can be called
   // to know if the data is target signal or interference and process it