Touch radius should be scaled to account for browser zoom.

Simple matter of applying the page zoom factor to the event.

TEST=fast/events/touch/touch-browser-zoom-scales-radius.html
BUG=230076

Review URL: https://codereview.chromium.org/107293003

git-svn-id: svn://svn.chromium.org/blink/trunk@163658 bbb929c8-8fbe-4397-9dbb-9b2b20218538