Mac: Prevent an NSException from being thrown in -getURLs:andTitles:.
Mac: Prevent an NSException from being thrown in -getURLs:andTitles:.

Code shouldn't assume that any given pasteboard type that is promised will
actually be provided.

This "fixes" bug 42420, though kind of incidentally. More importantly, it fixes
a crasher.

Possibly, this should be upstreamed back into Camino.

BUG=42420
TEST=dragging a bookmarklet (e.g., at <http://delicious.com/help/bookmarklets>) from web content to the bookmark bar won't cause a crash

Review URL: http://codereview.chromium.org/1750016

git-svn-id: http://src.chromium.org/svn/trunk/src@45697 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 3009c64f20a9ba8c49ffd77650fc73086f7c0813
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