Fix OEMCrypto_LoadUsageEntry fuzzer

- Ensure OEMCrypto is in the correct state before invoking
  OEMCrypto_LoadUsageEntry.
- Do not use FuzzedDataProvider to parse usage_entry_number since it
  causes unexpected parsing results.

Merged from https://widevine-internal-review.googlesource.com/168859
Merged from https://widevine-internal-review.googlesource.com/169293
Merged from https://widevine-internal-review.googlesource.com/169970
Merged from https://widevine-internal-review.googlesource.com/170011

Change-Id: I6c3ddfe457facef9c9d0fc524fc3cf76aba90f64

libwvdrmengine/oemcrypto/test/fuzz_tests/oemcrypto_load_usage_entry_fuzz.cc

@@ -2,22 +2,22 @@
 // source code may only be used and distributed under the Widevine Master
 // License Agreement.
 
-#include "FuzzedDataProvider.h"
 #include "OEMCryptoCENC.h"
 #include "oemcrypto_fuzz_helper.h"
 
 namespace wvoec {
 
+LicenseWithUsageEntryFuzz entry;
+
 OEMCryptoResult LoadUsageEntryWithFuzzedData(OEMCrypto_SESSION session,
                                              const uint8_t* data, size_t size) {
-  if (size < sizeof(uint32_t)) {
+  uint32_t usage_entry_number;
+  if (size < sizeof(usage_entry_number)) {
     return OEMCrypto_ERROR_SHORT_BUFFER;
   }
-
-  FuzzedDataProvider fuzzed_data(data, size);
-  const uint32_t usage_entry_number = fuzzed_data.ConsumeIntegral<uint32_t>();
-  const std::vector<uint8_t> buffer =
-      fuzzed_data.ConsumeRemainingBytes<uint8_t>();
+  memcpy(&usage_entry_number, data, sizeof(usage_entry_number));
+  const std::vector<uint8_t> buffer(data + sizeof(usage_entry_number),
+                                    data + size);
   return OEMCrypto_LoadUsageEntry(session, usage_entry_number, buffer.data(),
                                   buffer.size());
 }
@@ -25,7 +25,6 @@ OEMCryptoResult LoadUsageEntryWithFuzzedData(OEMCrypto_SESSION session,
 // The custom mutator to mutate created encrypted usage entry.
 extern "C" size_t LLVMFuzzerCustomMutator(uint8_t* data, size_t size,
                                           size_t max_size, unsigned int seed) {
-  LicenseWithUsageEntryFuzz entry;
   entry.CreateUsageTableHeader();
   Session* s = entry.license_messages().session();
   s->open();