Enable hidpi on Linux, refactor a bit on Windows to share

ui/aura/demo/demo_main.cc

 // Copyright (c) 2012 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 "base/at_exit.h"
 #include "base/command_line.h"
 #include "base/i18n/icu_util.h"
 #include "base/memory/scoped_ptr.h"
 #include "base/message_loop/message_loop.h"
 #include "third_party/skia/include/core/SkXfermode.h"
 #include "ui/aura/client/default_capture_client.h"
 #include "ui/aura/client/window_tree_client.h"
 #include "ui/aura/env.h"
 #include "ui/aura/test/test_focus_client.h"
 #include "ui/aura/test/test_screen.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_delegate.h"
 #include "ui/aura/window_tree_host.h"
 #include "ui/base/hit_test.h"
 #include "ui/compositor/test/in_process_context_factory.h"
 #include "ui/events/event.h"
 #include "ui/gfx/canvas.h"
+#include "ui/gfx/dpi.h"
 #include "ui/gfx/rect.h"
 #include "ui/gl/gl_surface.h"
 
 #if defined(USE_X11)
 #include "ui/gfx/x/x11_connection.h"
 #endif
 
-#if defined(OS_WIN)
-#include "ui/gfx/win/dpi.h"
-#endif
-
 namespace {
 
 // Trivial WindowDelegate implementation that draws a colored background.
 class DemoWindowDelegate : public aura::WindowDelegate {
  public:
   explicit DemoWindowDelegate(SkColor color) : color_(color) {}
 
   // Overridden from WindowDelegate:
   virtual gfx::Size GetMinimumSize() const override {
     return gfx::Size();
@@ skipping 65 matching lines @@
 
 int DemoMain() {
 #if defined(USE_X11)
   // This demo uses InProcessContextFactory which uses X on a separate Gpu
   // thread.
   gfx::InitializeThreadedX11();
 #endif
 
   gfx::GLSurface::InitializeOneOff();
 
-#if defined(OS_WIN)
+#if defined(OS_WIN) || (defined(OS_LINUX) && !defined(OS_CHROMEOS))
   gfx::InitDeviceScaleFactor(1.0f);
 #endif
 
   // The ContextFactory must exist before any Compositors are created.
   scoped_ptr<ui::InProcessContextFactory> context_factory(
       new ui::InProcessContextFactory());
 
   // Create the message-loop here before creating the root window.
   base::MessageLoopForUI message_loop;
 
@@ skipping 45 matching lines @@
 int main(int argc, char** argv) {
   CommandLine::Init(argc, argv);
 
   // The exit manager is in charge of calling the dtors of singleton objects.
   base::AtExitManager exit_manager;
 
   base::i18n::InitializeICU();
 
   return DemoMain();
 }