Ensure that pointer lock works correctly in Windows 7+ with HiDPI scale factors above 1
We were not scaling the mouse coordinate by the scale factor before invoking the ClientToScreen API. With this
change the blink::WebMouseEvent.globalX and globalY values have to be converted back to DIP after convering them to screen.
This should fix the mouse locking issue.
BUG=411634
TEST= The main test case in bug 411634
Review URL: https://codereview.chromium.org/
973123003
Cr-Commit-Position: refs/heads/master@{#319181}