Reland "Reland Process 8 kHz audio as 16 kHz internally of the audio processing module"

This is a reland of b7b8e30cb44c41f51dbbefb9a9160e6dfe869c5b

Original change's description:
> Reland Process 8 kHz audio as 16 kHz internally of the audio processing module
> 
> This CL relands the code from the CL "Process 8 kHz audio as 16 kHz internally
> of the audio processing module" which by mistake was reverted via a rebase in
> another CL.
> 
> The CL changes the behavior of APM for 8 kHz so that it is internally
> processed as 16 kHz.
> 
> Bug: webrtc:10863
> Change-Id: I32a57b2d279c2134125667c19b09cfda381a33c3
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150221
> Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
> Commit-Queue: Per Åhgren <peah@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#28944}

Bug: webrtc:10863
Change-Id: Ic626b99b099248f0d8a677dc4cfe1505e14ae7cd
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/150330
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Reviewed-by: Sam Zackrisson <saza@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#28949}
diff --git a/modules/audio_processing/audio_processing_unittest.cc b/modules/audio_processing/audio_processing_unittest.cc
index 831799f..461236e 100644
--- a/modules/audio_processing/audio_processing_unittest.cc
+++ b/modules/audio_processing/audio_processing_unittest.cc
@@ -1200,8 +1200,8 @@
 
 TEST_F(ApmTest, NoProcessingWhenAllComponentsDisabledFloat) {
   // Test that ProcessStream copies input to output even with no processing.
-  const size_t kSamples = 80;
-  const int sample_rate = 8000;
+  const size_t kSamples = 160;
+  const int sample_rate = 16000;
   const float src[kSamples] = {-1.0f, 0.0f, 1.0f};
   float dest[kSamples] = {};