Fix handling of store-write failures in Pver4

components/safe_browsing_db/v4_store.cc

 // Copyright 2016 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 "base/base64.h"
 #include "base/bind.h"
 #include "base/files/file_util.h"
 #include "base/memory/ptr_util.h"
 #include "base/metrics/histogram_macros.h"
 #include "base/metrics/sparse_histogram.h"
@@ skipping 720 matching lines @@
 
   // Attempt writing to a temporary file first and at the end, swap the files.
   const base::FilePath new_filename = TemporaryFileForFilename(store_path_);
 
   file_format.set_magic_number(kFileMagic);
   file_format.set_version_number(kFileVersion);
   std::string file_format_string;
   file_format.SerializeToString(&file_format_string);
   size_t written = base::WriteFile(new_filename, file_format_string.data(),
                                    file_format_string.size());
-  DCHECK_EQ(file_format_string.size(), written);
+
+  if (file_format_string.size() != written) {
+    return UNEXPECTED_BYTES_WRITTEN_FAILURE;
+  }
 
   if (!base::Move(new_filename, store_path_)) {
     return UNABLE_TO_RENAME_FAILURE;
   }
 
   // Update |file_size_| now because we wrote the file correctly.
   file_size_ = static_cast<int64_t>(written);
 
   return WRITE_SUCCESS;
 }
@@ skipping 99 matching lines @@
       base_metric + suffix, 1, 1000000, 50,
       base::HistogramBase::kUmaTargetedHistogramFlag);
   if (histogram) {
     const int64_t file_size_kilobytes = file_size_ / 1024;
     histogram->Add(file_size_kilobytes);
   }
   return file_size_;
 }
 
 }  // namespace safe_browsing