Fix WidgetBase::BlinkSpaceToFlooredDIPs

This method was introduced in https://crrev.com/c/2424066 but it missed
reversing the scale factor before scaling.

Bug: 1097816
Change-Id: I50231345b272028ba162dd4a69db6e0179a8612a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2444320
Commit-Queue: Dave Tapuska <dtapuska@chromium.org>
Reviewed-by: Dave Tapuska <dtapuska@chromium.org>
Cr-Commit-Position: refs/heads/master@{#813189}

third_party/blink/renderer/platform/widget/widget_base.cc

@@ -1286,8 +1286,8 @@ gfx::Point WidgetBase::BlinkSpaceToFlooredDIPs(const gfx::Point& point) {
     return point;
   // TODO(danakj): Should this be GetScreenInfo() so it changes under emulation?
   // TODO(dtapuska): Determine if this should be a floor vs rounded.
-  return gfx::ScaleToFlooredPoint(
-      point, client_->GetOriginalScreenInfo().device_scale_factor);
+  float reverse = 1 / client_->GetOriginalScreenInfo().device_scale_factor;
+  return gfx::ScaleToFlooredPoint(point, reverse);
 }
 
 gfx::Size WidgetBase::DIPsToCeiledBlinkSpace(const gfx::Size& size) {