Make WebHistoryItem serialization include the documentSequenceNumber.
Make WebHistoryItem serialization include the documentSequenceNumber.

This is a slight variation of http://codereview.chromium.org/556057.
In this CL, I change WriteHistoryItem to switch on kVersion to decide
whether or not to write out the documentSequenceNumber.  This seemed
better than my previous solution of appending documentSequenceNumber.

TBR=sky
BUG=none
TEST=none

Review URL: http://codereview.chromium.org/549196

git-svn-id: http://src.chromium.org/svn/trunk/src@37460 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

Former-commit-id: 7441af04f548dd00aaf1c4cc7796f8c7619276b0
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