Remove WebFloatPoint and use gfx::PointF

Now that WebInputEvent has moved off the usage of WebFloatPoint remove
the remaining usages.

The definition of WebFloatPoint adds nothing and using
gfx::PointF aligns with other uses of the gfx namespace in blink.

BUG=1008303
TBR=brucedawson@chromium.org

Change-Id: I837c77bdd9eb4b53c89f7cc534075a9bf5033b52
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1976562
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: David Bokan <bokan@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>
Reviewed-by: Avi Drissman <avi@chromium.org>
Reviewed-by: Jeremy Roman <jbroman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726841}
80 files changed