Revert of mus: Fix event transformation in client code.

ui/views/mus/window_tree_host_mus.cc

Index: ui/views/mus/window_tree_host_mus.cc
diff --git a/ui/views/mus/window_tree_host_mus.cc b/ui/views/mus/window_tree_host_mus.cc
index 24325157289de05f446f6a7fbba3ddce4d2d56f6..c388453e23044cf4990921f9d9f011864cd4dd38 100644
--- a/ui/views/mus/window_tree_host_mus.cc
+++ b/ui/views/mus/window_tree_host_mus.cc
@@ -24,6 +24,11 @@
       show_state_(ui::PLATFORM_WINDOW_STATE_UNKNOWN) {
   SetPlatformWindow(
       base::WrapUnique(new PlatformWindowMus(this, connector, window)));
+  // The location of events is already transformed, and there is no way to
+  // correctly determine the reverse transform. So, don't attempt to transform
+  // event locations, else the root location is wrong.
+  // TODO(sky): we need to transform for device scale though.
+  dispatcher()->set_transform_events(false);
   compositor()->SetHostHasTransparentBackground(true);
 
   input_method_.reset(new InputMethodMUS(this, window));