X11: Add TestDesktopScreenX11 to simulate mouse movement in ui tests

ui/views/test/test_desktop_screen_x11.h

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef UI_VIEWS_TEST_TEST_DESKTOP_SCREEN_X11_H_
+#define UI_VIEWS_TEST_TEST_DESKTOP_SCREEN_X11_H_
+
+#include "ui/gfx/geometry/point.h"
+#include "ui/views/widget/desktop_aura/desktop_screen_x11.h"
+
+namespace base {
+template<typename T> struct DefaultSingletonTraits;
+}
+
+namespace views {
+namespace test {
+
+// Replaces the screen instance in Linux (non-ChromeOS) tests.  Allows
+// aura tests to manually set the cursor screen point to be reported
+// by GetCursorScreenPoint().  Needed because of a limitation in the
+// X11 protocol that restricts us from warping the pointer with the
+// mouse button held down.
+class TestDesktopScreenX11 : public DesktopScreenX11 {
+ public:
+  static TestDesktopScreenX11* GetInstance();
+
+  TestDesktopScreenX11();
+  ~TestDesktopScreenX11() override;
+
+  gfx::Point GetCursorScreenPoint() override;

[sky, 2016/09/09 15:25:35]

Generally we prefix overrides with where the override comes from, e.g.
// DesktopScreenX11:
gfx::Point GetCursorScreenPoint() override;

Also, newline between 30/31.

[Tom (Use chromium acct), 2016/09/09 21:23:17]

Done.

+  void SetCursorScreenPoint(const gfx::Point& point);

[sky, 2016/09/09 15:25:35]

optional: We generally inline trivial functions like this (and then name using
unix_hacker_style), in this case set_cursor_screen_point.

[Tom (Use chromium acct), 2016/09/09 21:23:17]

Done.

+
+ private:
+  friend struct base::DefaultSingletonTraits<TestDesktopScreenX11>;
+
+  gfx::Point cursor_screen_point_;
+
+  DISALLOW_COPY_AND_ASSIGN(TestDesktopScreenX11);
+};
+
+}  // namespace test
+}  // namespace views
+
+#endif  // UI_VIEWS_TEST_TEST_DESKTOP_SCREEN_X11_H_