aura: Unify WindowTreeHost for some platforms

ash/host/ash_window_tree_host_win.cc

Index: ash/host/ash_window_tree_host_win.cc
diff --git a/ash/host/ash_window_tree_host_win.cc b/ash/host/ash_window_tree_host_win.cc
index e69769ca6a55fe8e3f789ad0bfb5c5252ccd98e4..203a5a7145465a06efdc2929dfbb9fd93c001180 100644
--- a/ash/host/ash_window_tree_host_win.cc
+++ b/ash/host/ash_window_tree_host_win.cc
@@ -13,7 +13,7 @@
 #include "ash/ime/input_method_event_handler.h"
 #include "base/command_line.h"
 #include "base/win/windows_version.h"
-#include "ui/aura/window_tree_host_win.h"
+#include "ui/aura/window_tree_host_platform.h"
 #include "ui/events/event_processor.h"
 #include "ui/gfx/geometry/insets.h"
 #include "ui/gfx/transform.h"
@@ -22,10 +22,10 @@ namespace ash {
 namespace {
 
 class AshWindowTreeHostWin : public AshWindowTreeHost,
-                             public aura::WindowTreeHostWin {
+                             public aura::WindowTreeHostPlatform {
  public:
   explicit AshWindowTreeHostWin(const gfx::Rect& initial_bounds)
-      : aura::WindowTreeHostWin(initial_bounds),
+      : aura::WindowTreeHostPlatform(initial_bounds),
         fullscreen_(false),
         saved_window_style_(0),
         saved_window_ex_style_(0),
@@ -40,29 +40,33 @@ class AshWindowTreeHostWin : public AshWindowTreeHost,
     gfx::Rect target_rect;
     if (!fullscreen_) {
       fullscreen_ = true;
-      saved_window_style_ = GetWindowLong(hwnd(), GWL_STYLE);
-      saved_window_ex_style_ = GetWindowLong(hwnd(), GWL_EXSTYLE);
-      GetWindowRect(hwnd(), &saved_window_rect_);
-      SetWindowLong(hwnd(),
+      saved_window_style_ = GetWindowLong(GetAcceleratedWidget(), GWL_STYLE);
+      saved_window_ex_style_ =
+          GetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE);
+      GetWindowRect(GetAcceleratedWidget(), &saved_window_rect_);
+      SetWindowLong(GetAcceleratedWidget(),
                     GWL_STYLE,
                     saved_window_style_ & ~(WS_CAPTION | WS_THICKFRAME));
       SetWindowLong(
-          hwnd(),
+          GetAcceleratedWidget(),
           GWL_EXSTYLE,
           saved_window_ex_style_ & ~(WS_EX_DLGMODALFRAME | WS_EX_WINDOWEDGE |
                                      WS_EX_CLIENTEDGE | WS_EX_STATICEDGE));
 
       MONITORINFO mi;
       mi.cbSize = sizeof(mi);
-      GetMonitorInfo(MonitorFromWindow(hwnd(), MONITOR_DEFAULTTONEAREST), &mi);
+      GetMonitorInfo(
+          MonitorFromWindow(GetAcceleratedWidget(), MONITOR_DEFAULTTONEAREST),
+          &mi);
       target_rect = gfx::Rect(mi.rcMonitor);
     } else {
       fullscreen_ = false;
-      SetWindowLong(hwnd(), GWL_STYLE, saved_window_style_);
-      SetWindowLong(hwnd(), GWL_EXSTYLE, saved_window_ex_style_);
+      SetWindowLong(GetAcceleratedWidget(), GWL_STYLE, saved_window_style_);
+      SetWindowLong(GetAcceleratedWidget(), GWL_EXSTYLE,
+                    saved_window_ex_style_);
       target_rect = gfx::Rect(saved_window_rect_);
     }
-    SetWindowPos(hwnd(),
+    SetWindowPos(GetAcceleratedWidget(),
                  NULL,
                  target_rect.x(),
                  target_rect.y(),