Fix error handling in POSIX version of the base::File::GetLength.

components/subresource_filter/core/browser/ruleset_service.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 "components/subresource_filter/core/browser/ruleset_service.h"
 
 #include <utility>
 
 #include "base/bind.h"
 #include "base/callback.h"
@@ skipping 328 matching lines @@
   DCHECK(indexed_version.IsValid());
   return indexed_version;
 }
 
 // static
 bool RulesetService::IndexRuleset(base::File unindexed_ruleset_file,
                                   RulesetIndexer* indexer) {
   SCOPED_UMA_HISTOGRAM_TIMER("SubresourceFilter.IndexRuleset.WallDuration");
 
   int64_t unindexed_ruleset_size = unindexed_ruleset_file.GetLength();
+  if (unindexed_ruleset_size < 0)
+    return false;
   CopyingFileInputStream copying_stream(std::move(unindexed_ruleset_file));
   google::protobuf::io::CopyingInputStreamAdaptor zero_copy_stream_adaptor(
       &copying_stream, 4096 /* buffer_size */);
   UnindexedRulesetReader reader(&zero_copy_stream_adaptor);
 
   size_t num_unsupported_rules = 0;
   proto::FilteringRules ruleset_chunk;
   while (reader.ReadNextChunk(&ruleset_chunk)) {
     for (const proto::UrlRule& rule : ruleset_chunk.url_rules()) {
       if (!indexer->AddUrlRule(rule))
@@ skipping 134 matching lines @@
   // version. Bail out.
   DCHECK(ruleset_data_);
   if (!ruleset_data_->IsValid())
     return;
 
   DCHECK_EQ(error, base::File::Error::FILE_OK);
   delegate_->PublishNewRulesetVersion(ruleset_data_->DuplicateFile());
 }
 
 }  // namespace subresource_filter