Set range of GetLinearAecOutput to [-1, 1]

The output of GetLinearAecOutput is changed to have the range [-1, 1]
instead of [-2^15, 2^15] to be more similar to other Audio Processing
Module API functions.

The "--linear_aec_output" of audioproc_f has been tested for
bit-exactness.

Bug: webrtc:12185
Change-Id: Id50d93fcfaee5c239f3eb73f99d0bd3533319518
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/193062
Reviewed-by: Per Åhgren <peah@webrtc.org>
Commit-Queue: Gustaf Ullberg <gustaf@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32604}

modules/audio_processing/audio_processing_impl.cc

@@ -1476,8 +1476,8 @@ bool AudioProcessingImpl::GetLinearAecOutput(
       rtc::ArrayView<const float> channel_view =
           rtc::ArrayView<const float>(linear_aec_buffer->channels_const()[ch],
                                       linear_aec_buffer->num_frames());
-      std::copy(channel_view.begin(), channel_view.end(),
-                linear_output[ch].begin());
+      FloatS16ToFloat(channel_view.data(), channel_view.size(),
+                      linear_output[ch].data());
     }
     return true;
   }

modules/audio_processing/test/audio_processing_simulator.cc

@@ -59,7 +59,6 @@ EchoCanceller3Config ReadAec3ConfigFromJsonFile(const std::string& filename) {
   return cfg;
 }
 
-
 std::string GetIndexedOutputWavFilename(const std::string& wav_name,
                                         int counter) {
   rtc::StringBuilder ss;
@@ -260,8 +259,8 @@ void AudioProcessingSimulator::ProcessStream(bool fixed_interface) {
     for (size_t k = 0; k < linear_aec_output_buf_[0].size(); ++k) {
       for (size_t ch = 0; ch < linear_aec_output_buf_.size(); ++ch) {
         RTC_CHECK_EQ(linear_aec_output_buf_[ch].size(), 160);
-        linear_aec_output_file_writer_->WriteSamples(
-            &linear_aec_output_buf_[ch][k], 1);
+        float sample = FloatToFloatS16(linear_aec_output_buf_[ch][k]);
+        linear_aec_output_file_writer_->WriteSamples(&sample, 1);
       }
     }
   }