Fix incorrectly added history entries on script-triggered location change.

committedMultipleRealLoads, given how it's used, should only be set when the second load creates a new history item.

BUG=323574
TEST=Tested manually on google spreadsheets, will land automated test in a separate patch

Review URL: https://codereview.chromium.org/109283002

git-svn-id: svn://svn.chromium.org/blink/trunk@163447 bbb929c8-8fbe-4397-9dbb-9b2b20218538