Add a check in the BlockBuffer of AEC2 to guard for buffer overflows.

webrtc/modules/audio_processing/aec/aec_core.cc

Index: webrtc/modules/audio_processing/aec/aec_core.cc
diff --git a/webrtc/modules/audio_processing/aec/aec_core.cc b/webrtc/modules/audio_processing/aec/aec_core.cc
index 3155bad9728dfbe9d051492ca183c8859b02cfa3..f64617e5db0505fbd10aed29f20aab21ca91a641 100644
--- a/webrtc/modules/audio_processing/aec/aec_core.cc
+++ b/webrtc/modules/audio_processing/aec/aec_core.cc
@@ -206,15 +206,18 @@ void BlockBuffer::ExtractExtendedBlock(float extended_block[PART_LEN2]) {
 
   // Extract the previous block.
   WebRtc_MoveReadPtr(buffer_, -1);
-  WebRtc_ReadBuffer(buffer_, reinterpret_cast<void**>(&block_ptr),
-                    &extended_block[0], 1);
+  size_t read_elements = WebRtc_ReadBuffer(
+      buffer_, reinterpret_cast<void**>(&block_ptr), &extended_block[0], 1);
+  RTC_CHECK_EQ(read_elements, 1);
   if (block_ptr != &extended_block[0]) {
     memcpy(&extended_block[0], block_ptr, PART_LEN * sizeof(float));
   }
 
   // Extract the current block.
-  WebRtc_ReadBuffer(buffer_, reinterpret_cast<void**>(&block_ptr),
-                    &extended_block[PART_LEN], 1);
+  read_elements =
+      WebRtc_ReadBuffer(buffer_, reinterpret_cast<void**>(&block_ptr),
+                        &extended_block[PART_LEN], 1);
+  RTC_CHECK_EQ(read_elements, 1);
   if (block_ptr != &extended_block[PART_LEN]) {
     memcpy(&extended_block[PART_LEN], block_ptr, PART_LEN * sizeof(float));
   }