Update OEMCrypto test comments and logs

Merge from Widevine repo of http://go/wvgerrit/121886

This CL merges some changes from branch rvc-dev to sc-dev
that prepared it for merge.

One change is that the unit tests now say they are part of
Android S instead of R.

Bug: 180546871
Change-Id: I2ebbd8f7b8586389ebb75f3743a2dc2ad8caa214

libwvdrmengine/oemcrypto/test/fuzz_tests/oemcrypto_decrypt_cenc_fuzz.cc

@@ -7,6 +7,7 @@
 #include "log.h"
 #include "oemcrypto_fuzz_helper.h"
 #include "oemcrypto_fuzz_structs.h"
+#include "oemcrypto_overflow.h"
 
 namespace wvoec {
 const size_t MAX_FUZZ_SAMPLE_SIZE = 5 * MB;
@@ -137,13 +138,16 @@ extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
 
     // Copy sub sample data.
     sample_descriptions[i].subsamples = &subsamples[input_subsample_index];
-    input_subsample_index += sample_descriptions[i].subsamples_length;
+    if (AddOverflowUX(input_subsample_index,
+                      sample_descriptions[i].subsamples_length,
+                      &input_subsample_index)) {
+      return 0;
+    }
     if (input_subsample_index > subsamples.size()) return 0;
   }  // Sample loop.
 
   // Allocate input/output buffers for each sample description.
   vector<OEMCrypto_SharedMemory> input_buffer(total_input_data_length);
-  RAND_bytes(input_buffer.data(), total_input_data_length);
   size_t input_buffer_index = 0;
   for (size_t i = 0; i < samples_length; i++) {
     sample_descriptions[i].buffers.input_data =