Add a prompt line to the "Bookmark All Tabs" sheet so that the user knows what's going on if they accidentally invoke this via Cmd-Shift-D.  BUG=59238 Review URL: http://codereview.chromium.org/6372009
Add a prompt line to the "Bookmark All Tabs" sheet so that the user knows what's going on if they accidentally invoke this via Cmd-Shift-D. 
BUG=59238
Review URL: http://codereview.chromium.org/6372009

git-svn-id: http://src.chromium.org/svn/trunk/src@72193 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 0a65dc4c681fbcf5513ac7e8839b0398d346ee31
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