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

ui/gfx/dpi_linux.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 "ui/gfx/dpi.h"
+
+#include "ui/gfx/linux_font_delegate.h"
+
+namespace gfx {
+
+Size GetDPI() {
+  static int dpi = 0;
+  static bool should_initialize = true;
+
+  if (should_initialize) {
+    const gfx::LinuxFontDelegate* delegate = gfx::LinuxFontDelegate::instance();
+    if (delegate)
+      dpi = delegate->GetFontDPI();
+    if (dpi <= 0)
+      dpi = 96;
+  }
+  return Size(dpi, dpi);
+}
+
+bool IsHighDPIEnabled() {
+#if defined(OS_LINUX)

[sky, 2014/10/22 21:11:18]

This ifdef shouldn't be necessary, right?

[scottmg, 2014/10/22 23:56:18]

Done.

+  return true;
+#endif
+}
+
+}  // namespace gfx