cros: Fix a comparison of a bool with -1

BUG=none
TBR=bshe

Review URL: https://codereview.chromium.org/11419315

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@171023 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/chromeos/extensions/wallpaper_private_api.cc

@@ -90,7 +90,7 @@ bool GetData(int key, const std::string& file_name, std::string* data) {
   FilePath file_path = data_dir.Append(file_name);
 
   return !file_util::PathExists(file_path) ||
-         (file_util::ReadFileToString(file_path, data) != -1);
+         !file_util::ReadFileToString(file_path, data);
 }
 
 class WindowStateManager;