Remove some ifdefs from ash since it only supports ChromeOS now.

ash/display/mirror_window_controller.cc

Index: ash/display/mirror_window_controller.cc
diff --git a/ash/display/mirror_window_controller.cc b/ash/display/mirror_window_controller.cc
index b0e2d24f58708b56af2c74c3faee2a115031379d..0673b8f7ac1c19e7f1b55cc7c796b6fd3a24352e 100644
--- a/ash/display/mirror_window_controller.cc
+++ b/ash/display/mirror_window_controller.cc
@@ -6,13 +6,11 @@
 
 #include <utility>
 
-#if defined(USE_X11)
 #include <X11/extensions/XInput2.h>
 #include <X11/Xlib.h>
 
 // Xlib.h defines RootWindow.
 #undef RootWindow
-#endif
 
 #include "ash/display/cursor_window_controller.h"
 #include "ash/display/root_window_transformers.h"
@@ -30,6 +28,7 @@
 #include "ui/aura/window_delegate.h"
 #include "ui/aura/window_event_dispatcher.h"
 #include "ui/aura/window_tree_host.h"
+#include "ui/aura/window_tree_host_x11.h"
 #include "ui/base/layout.h"
 #include "ui/compositor/reflector.h"
 #include "ui/display/display_layout.h"
@@ -38,11 +37,7 @@
 #include "ui/display/screen.h"
 #include "ui/gfx/canvas.h"
 #include "ui/gfx/native_widget_types.h"
-
-#if defined(USE_X11)

[Evan Stade, 2017/01/13 17:19:34]

Am I correct in thinking OS_CHROMEOS implies USE_X11? It seems the only linux
config that doesn't use x11 is chromecast.

[James Cook, 2017/01/13 20:19:31]

No, real Chromebooks don't run X. They use our own Ozone code backed directly by
the Linux kernel DRM system. So we still need these ifdefs.

[Evan Stade, 2017/01/19 00:36:21]

ah, ok. restored

-#include "ui/aura/window_tree_host_x11.h"
 #include "ui/gfx/x/x11_types.h"  // nogncheck
-#endif
 
 namespace ash {
 namespace {
@@ -193,14 +188,11 @@ void MirrorWindowController::UpdateWindow(
       InitRootWindowSettings(host->window())->display_id = display_info.id();
       host->InitHost();
       host->window()->Show();
-#if defined(USE_X11)
       if (!display_manager->IsInUnifiedMode()) {
         // Mirror window shouldn't handle input events.
         static_cast<aura::WindowTreeHostX11*>(host)->DisableInput();
       }
-#endif
 
-#if defined(OS_CHROMEOS)
       if (display_manager->IsInUnifiedMode()) {
         host_info->ash_host->ConfineCursorToRootWindow();
         AshWindowTreeHost* unified_ash_host =
@@ -212,7 +204,6 @@ void MirrorWindowController::UpdateWindow(
         aura::client::SetScreenPositionClient(host->window(),
                                               screen_position_client_.get());
       }
-#endif
 
       aura::client::SetCaptureClient(host->window(), new NoneCaptureClient());
       host->Show();