chromeos: fix infinite loop in cursor lookup

And remove a NOTREACHED that we're hitting. I will supply a test for this
separate, as well as investgating removal of NOREACHED.

BUG=855767
TEST=none

Change-Id: Idf59b80388fefa06317a70055d18db995187c9a0
Reviewed-on: https://chromium-review.googlesource.com/1134352Reviewed-by: Michael Wasserman <msw@chromium.org>
Commit-Queue: Scott Violet <sky@chromium.org>
Cr-Commit-Position: refs/heads/master@{#574371}

services/ui/ws2/window_delegate_impl.cc

@@ -35,6 +35,8 @@ gfx::NativeCursor WindowDelegateImpl::GetCursor(const gfx::Point& point) {
        server_window; server_window = ServerWindow::GetMayBeNull(
                           server_window->window()->parent())) {
     if (server_window->IsTopLevel()) {
+      if (server_window->window() == window_)
+        return server_window->cursor();
       gfx::Point toplevel_point = point;
       aura::Window::ConvertPointToTarget(window_, server_window->window(),
                                          &toplevel_point);
@@ -45,7 +47,8 @@ gfx::NativeCursor WindowDelegateImpl::GetCursor(const gfx::Point& point) {
       return server_window->cursor();
   }
 
-  NOTREACHED();
+  // TODO(sky): there should be a NOTREACHED() here, but we're hitting this on
+  // asan builder. Figure out. https://crbug.com/855767.
   return gfx::kNullCursor;
 }
 

services/ui/ws2/window_delegate_impl.h

@@ -11,8 +11,10 @@
 namespace ui {
 namespace ws2 {
 
-// The aura::WindowDelegate implementation used for non-top-level windows
-// created by the WindowService.
+// The aura::WindowDelegate implementation used by Windows created by the
+// WindowService. The local environment may create its own WindowDelegate for
+// top-level windows (by way of WindowServiceDelegate::NewTopLevel()).
+//
 // WindowDelegateImpl deletes itself when the associated window is deleted.
 class COMPONENT_EXPORT(WINDOW_SERVICE) WindowDelegateImpl
     : public aura::WindowDelegate {