mus: Implement ScreenMus::GetCursorScreenPoint().

ui/views/mus/screen_mus.cc

Index: ui/views/mus/screen_mus.cc
diff --git a/ui/views/mus/screen_mus.cc b/ui/views/mus/screen_mus.cc
index e281b97425988f0f053a1d8d38f841a958219f91..442db2ab1a1ee06c02e426008f242b7542a3b75b 100644
--- a/ui/views/mus/screen_mus.cc
+++ b/ui/views/mus/screen_mus.cc
@@ -80,7 +80,8 @@ namespace views {
 ScreenMus::ScreenMus(ScreenMusDelegate* delegate)
     : delegate_(delegate),
       primary_display_index_(0),
-      display_manager_observer_binding_(this) {}
+      display_manager_observer_binding_(this) {
+}
 
 ScreenMus::~ScreenMus() {}
 
@@ -160,8 +161,14 @@ void ScreenMus::ProcessDisplayChanged(const display::Display& changed_display,
 }
 
 gfx::Point ScreenMus::GetCursorScreenPoint() {
-  NOTIMPLEMENTED();
-  return gfx::Point();
+  if (!delegate_) {
+    // TODO(erg): If we need the cursor point in the window manager, we'll need
+    // to make |delegate_| required. It only recently changed to be optional.
+    NOTIMPLEMENTED();
+    return gfx::Point();
+  }
+
+  return delegate_->GetCursorScreenPoint();
 }
 
 gfx::NativeWindow ScreenMus::GetWindowUnderCursor() {