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
===================================================================
--- ui/base/events/event.cc	(revision 185345)
+++ ui/base/events/event.cc	(working copy)
@@ -679,6 +679,17 @@
   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