Refactor cpu_features_wrapper.h functions from C to C++.

As mentioned on https://webrtc-review.googlesource.com/c/src/+/183380,
then relanded as https://webrtc-review.googlesource.com/c/src/+/183444,
functions in cpu_features_wrapper.h should be refactored to use
C++ features like namespaces and drop the WebRtc_ prefix.

Bug: None
Change-Id: I3e83e1668f9bf48a5d8e85d809f006666b7fa45e
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/183445
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32045}
diff --git a/modules/audio_processing/aec3/fft_data_unittest.cc b/modules/audio_processing/aec3/fft_data_unittest.cc
index b0235a7..d76fabd 100644
--- a/modules/audio_processing/aec3/fft_data_unittest.cc
+++ b/modules/audio_processing/aec3/fft_data_unittest.cc
@@ -20,7 +20,7 @@
 // Verifies that the optimized methods are bitexact to their reference
 // counterparts.
 TEST(FftData, TestSse2Optimizations) {
-  if (WebRtc_GetCPUInfo(kSSE2) != 0) {
+  if (GetCPUInfo(kSSE2) != 0) {
     FftData x;
 
     for (size_t k = 0; k < x.re.size(); ++k) {
@@ -43,7 +43,7 @@
 // Verifies that the optimized methods are bitexact to their reference
 // counterparts.
 TEST(FftData, TestAvx2Optimizations) {
-  if (WebRtc_GetCPUInfo(kAVX2) != 0) {
+  if (GetCPUInfo(kAVX2) != 0) {
     FftData x;
 
     for (size_t k = 0; k < x.re.size(); ++k) {