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This is needed as a prerequisite to making "visual viewport scrolls first"
the default. Scrolling the page before setting scale means that the layout
viewport is the only one that could scroll.

Note, this is patching 2 tests I missed in my original patch:
http://crrev.com/1301523006

BUG=443724
TBR=majidvp@chromium.org

Review URL: https://codereview.chromium.org/1317003002

git-svn-id: svn://svn.chromium.org/blink/trunk@201236 bbb929c8-8fbe-4397-9dbb-9b2b20218538