Handle invalid usage cache file path

webkit/fileapi/file_system_usage_cache.cc

Index: webkit/fileapi/file_system_usage_cache.cc
diff --git a/webkit/fileapi/file_system_usage_cache.cc b/webkit/fileapi/file_system_usage_cache.cc
index 73f4cbed60881f53c05e8c71e6da706a4a0e81e6..f122378548122555656d8b1e35dd4655e6b1c1a8 100644
--- a/webkit/fileapi/file_system_usage_cache.cc
+++ b/webkit/fileapi/file_system_usage_cache.cc
@@ -130,9 +130,9 @@ int64 FileSystemUsageCache::Read(const FilePath& usage_file_path,
                                  uint32* dirty) {
   char buffer[kUsageFileSize];
   const char *header;
-  DCHECK(!usage_file_path.empty());
-  if (kUsageFileSize !=
-      file_util::ReadFile(usage_file_path, buffer, kUsageFileSize))
+  if (usage_file_path.empty() ||
+      kUsageFileSize != file_util::ReadFile(usage_file_path,
+                                            buffer, kUsageFileSize))
     return -1;
   Pickle read_pickle(buffer, kUsageFileSize);
   PickleIterator iter(read_pickle);
@@ -164,9 +164,9 @@ int FileSystemUsageCache::Write(const FilePath& usage_file_path,
   write_pickle.WriteUInt32(dirty);
   write_pickle.WriteInt64(fs_usage);
 
-  DCHECK(!usage_file_path.empty());
   FilePath temporary_usage_file_path;
-  if (!file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
+  if (usage_file_path.empty() ||
+      !file_util::CreateTemporaryFileInDir(usage_file_path.DirName(),
                                            &temporary_usage_file_path)) {
     return -1;
   }