Ensure that pointer lock works correctly in Windows 7+ with HiDPI scale factors above 1

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

Committed: https://crrev.com/05f7888960f6e3393b2ad5f5835028404737c584
Cr-Commit-Position: refs/heads/master@{#319181}

[ananta, 2015-03-04 02:59:43]

ananta@chromium.org changed reviewers:
+ scheib@chromium.org

[scheib, 2015-03-04 05:14:19]

Thanks, LGTM with one item:

Please add a TEST= line to the change description, probably referencing the bug
repro case.

[ananta, 2015-03-04 20:21:32]

ananta@chromium.org changed reviewers:
+ cpu@chromium.org

[ananta, 2015-03-04 20:21:32]

+cpu for owners

[cpu_(ooo_6.6-7.5), 2015-03-05 00:54:54]

lgtm

[cpu_(ooo_6.6-7.5), 2015-03-05 00:54:58]

The CQ bit was checked by cpu@chromium.org

[commit-bot: I haz the power, 2015-03-05 00:55:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/973123003/1

[commit-bot: I haz the power, 2015-03-05 01:01:57]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-05 01:03:08]

Patchset 1 (id:??) landed as
https://crrev.com/05f7888960f6e3393b2ad5f5835028404737c584
Cr-Commit-Position: refs/heads/master@{#319181}