Handle invalid usage cache file path

usage_file_path can be empty when a FileSystem is accessed after DeleteFileSystem call.

BUG=


Review URL: https://chromiumcodereview.appspot.com/10832316

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@151692 0039d316-1c4b-4281-b951-d872f2087c98

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;
   }