Add functions to interact with ASan and MSan, and some sample uses

webrtc/common_audio/signal_processing/downsample_fast.c

Index: webrtc/common_audio/signal_processing/downsample_fast.c
diff --git a/webrtc/common_audio/signal_processing/downsample_fast.c b/webrtc/common_audio/signal_processing/downsample_fast.c
index 726a88819ac01e47e3dbfb4e41ccd2739d2f3dcd..3cbc3c111a67fae19b6bc5dccec76882aeaa2d06 100644
--- a/webrtc/common_audio/signal_processing/downsample_fast.c
+++ b/webrtc/common_audio/signal_processing/downsample_fast.c
@@ -10,6 +10,9 @@
 
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 
+#include "webrtc/base/checks.h"
+#include "webrtc/base/sanitizer.h"
+
 // TODO(Bjornv): Change the function parameter order to WebRTC code style.
 // C version of WebRtcSpl_DownsampleFast() for generic platforms.
 int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
@@ -20,6 +23,7 @@ int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
                               size_t coefficients_length,
                               int factor,
                               size_t delay) {
+  int16_t* const original_data_out = data_out;
   size_t i = 0;
   size_t j = 0;
   int32_t out_s32 = 0;
@@ -31,10 +35,14 @@ int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
     return -1;
   }
 
+  rtc_MsanCheckInitialized(coefficients, sizeof(coefficients[0]),
+                           coefficients_length);
+
   for (i = delay; i < endpos; i += factor) {
     out_s32 = 2048;  // Round value, 0.5 in Q12.
 
     for (j = 0; j < coefficients_length; j++) {
+      rtc_MsanCheckInitialized(&data_in[i - j], sizeof(data_in[0]), 1);
       out_s32 += coefficients[j] * data_in[i - j];  // Q12.
     }
 
@@ -44,5 +52,9 @@ int WebRtcSpl_DownsampleFastC(const int16_t* data_in,
     *data_out++ = WebRtcSpl_SatW32ToW16(out_s32);
   }
 
+  RTC_DCHECK_EQ(original_data_out + data_out_length, data_out);
+  rtc_MsanCheckInitialized(original_data_out, sizeof(original_data_out[0]),
+                           data_out_length);
+
   return 0;
 }