Fix two unchecked return values

webkit/fileapi/file_system_usage_cache.cc

 // Copyright (c) 2012 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 "webkit/fileapi/file_system_usage_cache.h"
 
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/pickle.h"
 
@@ skipping 68 matching lines @@
   uint32 dirty = 0;
   int64 fs_usage;
   fs_usage = Read(usage_file_path, &is_valid, &dirty);
 
   return fs_usage >= 0 && Write(usage_file_path, false, dirty, fs_usage);
 }
 
 bool FileSystemUsageCache::IsValid(const FilePath& usage_file_path) {
   bool is_valid = true;
   uint32 dirty = 0;
-  Read(usage_file_path, &is_valid, &dirty);
+  int64 result = Read(usage_file_path, &is_valid, &dirty);
+  if (result < 0)
+    return false;
+
   return is_valid;
 }
 
 // static
 int FileSystemUsageCache::AtomicUpdateUsageByDelta(
     const FilePath& usage_file_path, int64 delta) {
   bool is_valid = true;
   uint32 dirty = 0;
   int64 fs_usage;
   // TODO(dmikurube): Make sure that usage_file_path is available.
@@ skipping 56 matching lines @@
                                 uint32 dirty,
                                 int64 fs_usage) {
   Pickle write_pickle;
   write_pickle.WriteBytes(kUsageFileHeader, kUsageFileHeaderSize);
   write_pickle.WriteBool(is_valid);
   write_pickle.WriteUInt32(dirty);
   write_pickle.WriteInt64(fs_usage);
 
   DCHECK(!usage_file_path.empty());
   FilePath temporary_usage_file_path;
-  file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
-                                      &temporary_usage_file_path);
+  if (!file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
+                                           &temporary_usage_file_path)) {
+    return -1;
+  }
+
   int bytes_written = file_util::WriteFile(temporary_usage_file_path,
                                            (const char *)write_pickle.data(),
                                            write_pickle.size());
   if (bytes_written != kUsageFileSize)
     return -1;
 
   if (file_util::ReplaceFile(temporary_usage_file_path, usage_file_path))
     return bytes_written;
   else
     return -1;
 }
 
 }  // namespace fileapi