Remove DisplayChangeObserver ash dependencies.

ui/display/chromeos/touchscreen_util_unittest.cc

Index: ui/display/chromeos/touchscreen_util_unittest.cc
diff --git a/ui/display/chromeos/touchscreen_util_unittest.cc b/ui/display/chromeos/touchscreen_util_unittest.cc
index c7f0195a5f8805e5af4f1d51cbe4630aa1a081d6..45aeae250961558043290c4afba8f4e730349557 100644
--- a/ui/display/chromeos/touchscreen_util_unittest.cc
+++ b/ui/display/chromeos/touchscreen_util_unittest.cc
@@ -30,8 +30,8 @@ class TouchscreenUtilTest : public testing::Test {
   // testing::Test:
   void SetUp() override {
     // Recreate for each test, DisplayManager has a lot of state.
-    display_manager_ =
-        base::MakeUnique<DisplayManager>(base::MakeUnique<ScreenBase>());
+    display_manager_ = base::MakeUnique<DisplayManager>(
+        base::MakeUnique<ScreenBase>(), nullptr);
 
     // Internal display will always match to internal touchscreen. If internal
     // touchscreen can't be detected, it is then associated to a touch screen