Tidy up to enable C4800 on Windows

minidump/minidump_file_writer.cc

 // Copyright 2014 The Crashpad Authors. All rights reserved.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
 //
 //     http://www.apache.org/licenses/LICENSE-2.0
 //
 // Unless required by applicable law or agreed to in writing, software
 // distributed under the License is distributed on an "AS IS" BASIS,
@@ skipping 155 matching lines @@
   if (file_writer->Seek(start_offset, SEEK_SET) != 0) {
     return false;
   }
 
   if (!file_writer->Write(&header_, sizeof(header_))) {
     return false;
   }
 
   // Seek back to the end of the file, in case some non-minidump content will be
   // written to the file after the minidump content.
-  return file_writer->Seek(end_offset, SEEK_SET);
+  return file_writer->Seek(end_offset, SEEK_SET) >= 0;
 }
 
 bool MinidumpFileWriter::Freeze() {
   DCHECK_EQ(state(), kStateMutable);
 
   if (!MinidumpWritable::Freeze()) {
     return false;
   }
 
   size_t stream_count = streams_.size();
@@ skipping 52 matching lines @@
   for (internal::MinidumpStreamWriter* stream : streams_) {
     iov.iov_base = stream->DirectoryListEntry();
     iov.iov_len = sizeof(MINIDUMP_DIRECTORY);
     iovecs.push_back(iov);
   }
 
   return file_writer->WriteIoVec(&iovecs);
 }
 
 }  // namespace crashpad