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

webrtc/common_audio/signal_processing/filter_ma_fast_q12.c

Index: webrtc/common_audio/signal_processing/filter_ma_fast_q12.c
diff --git a/webrtc/common_audio/signal_processing/filter_ma_fast_q12.c b/webrtc/common_audio/signal_processing/filter_ma_fast_q12.c
index f4d9a3d3038cf1480b4cf7cf8fdf3503245a8881..98f5b3cb6d4f2180bbfe621b688b261b8ff141d1 100644
--- a/webrtc/common_audio/signal_processing/filter_ma_fast_q12.c
+++ b/webrtc/common_audio/signal_processing/filter_ma_fast_q12.c
@@ -17,6 +17,8 @@
 
 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
 
+#include "webrtc/base/sanitizer.h"
+
 void WebRtcSpl_FilterMAFastQ12(const int16_t* in_ptr,
                                int16_t* out_ptr,
                                const int16_t* B,
@@ -24,6 +26,11 @@ void WebRtcSpl_FilterMAFastQ12(const int16_t* in_ptr,
                                size_t length)
 {
     size_t i, j;
+
+    rtc_MsanCheckInitialized(B, sizeof(B[0]), B_length);
+    rtc_MsanCheckInitialized(in_ptr - B_length + 1, sizeof(in_ptr[0]),
+                             B_length + length - 1);

[kwiberg-webrtc, 2016/08/30 19:55:28]

This is the sort of rtc_MsanCheckInitialized() call that one doesn't want to
see, since it shows that the code was written by crazy people who were
nevertheless brilliant since they got it to mostly work. However, removing it
would be like shooting the messenger and sweeping the body under the rug.

[hlundin-webrtc, 2016/09/01 13:41:35]

What?! You don't like functions that use memory "to the left" of the data
pointer given?

[kwiberg-webrtc, 2016/09/02 07:30:16]

Well, as long as you don't document what memory range your function accesses I
guess it's OK.

+
     for (i = 0; i < length; i++)
     {
         int32_t o = 0;