More refactoring for Viewer

tools/viewer/sk_app/Window.h

 /*
 * Copyright 2016 Google Inc.
 *
 * Use of this source code is governed by a BSD-style license that can be
 * found in the LICENSE file.
 */
 
 #ifndef Window_DEFINED
 #define Window_DEFINED
 
 #include "SkTypes.h"
 #include "SkRect.h"
 
 class SkCanvas;
-class VulkanTestContext;
 
 namespace sk_app {
 
+class WindowContext;
+
 class Window {
 public:
     static Window* CreateNativeWindow(void* platformData);
 
     virtual ~Window() {};
 
     virtual void setTitle(const char*) = 0;
     virtual void show() = 0;
     virtual void inval() = 0;
 
@@ skipping 107 matching lines @@
 
     OnCharFunc   fCharFunc;
     void*        fCharUserData;
     OnKeyFunc    fKeyFunc;
     void*        fKeyUserData;
     OnMouseFunc  fMouseFunc;
     void*        fMouseUserData;
     OnPaintFunc  fPaintFunc;
     void*        fPaintUserData;
 
-    VulkanTestContext* fTestContext;
+    WindowContext* fWindowContext;
 };
 
 }   // namespace sk_app
 #endif