Check that the PNaCl cache hash is truly derived from the bitcode content.

chrome/renderer/pepper/ppb_nacl_hash_private_impl.cc

+// Copyright (c) 2013 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/renderer/pepper/ppb_nacl_hash_private_impl.h"
+
+#ifndef DISABLE_NACL
+
+#include "crypto/secure_hash.h"
+#include "crypto/secure_util.h"
+#include "ppapi/c/pp_bool.h"
+
+namespace {
+
+void* CreateSHA256Hash() {
+  return static_cast<void*>(crypto::SecureHash::Create(
+      crypto::SecureHash::SHA256));
+}
+
+void Update(void* hasher, const void* data, uint32_t len) {
+  crypto::SecureHash* h = static_cast<crypto::SecureHash*>(hasher);
+  h->Update(data, len);
+}
+
+void Finish(void* hasher, void* output, uint32_t len) {
+  crypto::SecureHash* h = static_cast<crypto::SecureHash*>(hasher);
+  h->Finish(output, len);
+}
+
+void Delete(void* hasher) {
+  crypto::SecureHash* h = static_cast<crypto::SecureHash*>(hasher);
+  delete h;
+}
+
+PP_Bool SecureMemEqual(const char* h1, const char* h2, uint32_t len) {
+  return PP_FromBool(crypto::SecureMemEqual(h1, h2, len));
+}
+
+const PPB_NaCl_Hash_Private nacl_hash_interface = {
+  &CreateSHA256Hash,
+  &Update,
+  &Finish,
+  &Delete,
+  &SecureMemEqual
+};
+
+}  // namespace
+
+const PPB_NaCl_Hash_Private* PPB_NaCl_Hash_Private_Impl::GetInterface() {
+  return &nacl_hash_interface;
+}
+
+#endif  // DISABLE_NACL