events: Make sure the unaccelerated scroll deltas get adjusted properly for device-scale-factor.

ui/base/events/event.cc

Index: ui/base/events/event.cc
diff --git a/ui/base/events/event.cc b/ui/base/events/event.cc
index 079e5f7fa9f1baf0c56c1029d0f8ca4967dbde66..ad26a24744d63245cdbe49a6a02a171991f8541f 100644
--- a/ui/base/events/event.cc
+++ b/ui/base/events/event.cc
@@ -679,6 +679,17 @@ void ScrollEvent::Scale(const float factor) {
   y_offset_ordinal_ *= factor;
 }
 
+void ScrollEvent::UpdateForRootTransform(const gfx::Transform& root_transform) {
+  LocatedEvent::UpdateForRootTransform(root_transform);
+  gfx::DecomposedTransform decomp;
+  bool success = gfx::DecomposeTransform(&decomp, root_transform);
+  DCHECK(success);
+  if (decomp.scale[0])
+    x_offset_ordinal_ /= decomp.scale[0];
+  if (decomp.scale[1])
+    y_offset_ordinal_ /= decomp.scale[1];
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // GestureEvent