Make JoinString implementation match prototype.
Make JoinString implementation match prototype.

This fixes the linux shared build. Error was:

out/Release/lib.target/chrome/libbrowser.so: undefined reference to `JoinString(std::vector<std::basic_string<unsigned short, base::string16_char_traits, std::allocator<unsigned short> >, std::allocator<std::basic_string<unsigned short, base::string16_char_traits, std::allocator<unsigned short> > > > const&, unsigned short)'

Review URL: http://codereview.chromium.org/518037

git-svn-id: http://src.chromium.org/svn/trunk/src@35533 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: b2feca0488d9925dbb0fe30cf844670f0e6c8344
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