X11: Add TestDesktopScreenX11 to simulate mouse movement in ui tests

chrome/test/base/view_event_test_platform_part_default.cc

 // Copyright 2014 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.
 
 #include <memory>
 
 #include "base/macros.h"
 #include "chrome/test/base/view_event_test_platform_part.h"
 #include "ui/aura/env.h"
 #include "ui/display/screen.h"
 #include "ui/views/widget/desktop_aura/desktop_screen.h"
 
+#if !defined(OS_CHROMEOS) && defined(OS_LINUX)
+#include "ui/views/test/test_desktop_screen_x11.h"
+#endif
+
 namespace {
 
 // ViewEventTestPlatformPart implementation for Views, but non-CrOS.
 class ViewEventTestPlatformPartDefault : public ViewEventTestPlatformPart {
  public:
   explicit ViewEventTestPlatformPartDefault(
       ui::ContextFactory* context_factory) {
 #if defined(USE_AURA)
+    DCHECK(!display::Screen::GetScreen());
+#if !defined(OS_CHROMEOS) && defined(OS_LINUX)
+    display::Screen::SetScreenInstance(
+        views::test::TestDesktopScreenX11::GetInstance());
+#else
     screen_.reset(views::CreateDesktopScreen());
     display::Screen::SetScreenInstance(screen_.get());
+#endif
     env_ = aura::Env::CreateInstance();
     env_->set_context_factory(context_factory);
 #endif
   }
 
   ~ViewEventTestPlatformPartDefault() override {
 #if defined(USE_AURA)
     env_.reset();
     display::Screen::SetScreenInstance(nullptr);
 #endif
   }
 
   // Overridden from ViewEventTestPlatformPart:
   gfx::NativeWindow GetContext() override { return NULL; }
 
  private:
   std::unique_ptr<display::Screen> screen_;
   std::unique_ptr<aura::Env> env_;
 
   DISALLOW_COPY_AND_ASSIGN(ViewEventTestPlatformPartDefault);
 };
 
 }  // namespace
 
 // static
 ViewEventTestPlatformPart* ViewEventTestPlatformPart::Create(
     ui::ContextFactory* context_factory) {
   return new ViewEventTestPlatformPartDefault(context_factory);
 }