BrowserPlugin: loadabort on empty src.

If the src attribute is somehow empty (it shouldn't be in normal usage of
<webview>) then fire a loadabort so that the content embedder can react to
it instead of simply exiting early.

BUG=none
TBR=fsamuel@chromium.org

Review URL: https://codereview.chromium.org/104043009

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241301 0039d316-1c4b-4281-b951-d872f2087c98
Added new strings for the "Reset Settings" dialog.

BUG=324931
R=battre@chromium.org

Review URL: https://codereview.chromium.org/117283002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@241302 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 241302