Fixed the error when joining a list of _StackTraceLine instances.
Fixed the error when joining a list of _StackTraceLine instances.

TBR=timurrrr

Review URL: http://codereview.chromium.org/3583001

git-svn-id: http://src.chromium.org/svn/trunk/src@60931 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: c9d7237a52ee90d01717361dc4940ead0d31dc99
meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser,meego-tablet-ux/meego-app-browser