Refactor SkyShell to allow multiple SkyViews

sky/shell/android/platform_view_android.h

 // Copyright 2015 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.
 
 #ifndef SKY_SHELL_PLATFORM_VIEW_ANDROID_H_
 #define SKY_SHELL_PLATFORM_VIEW_ANDROID_H_
 
 #include "sky/shell/platform_view.h"
 
 struct ANativeWindow;
 
 namespace sky {
 namespace shell {
+class Instance;
 
 class PlatformViewAndroid : public PlatformView {
  public:
   static bool Register(JNIEnv* env);
+
+  PlatformViewAndroid(const Config& config);
   ~PlatformViewAndroid() override;
 
   // Called from Java
   void Detach(JNIEnv* env, jobject obj);
   void SurfaceCreated(JNIEnv* env, jobject obj, jobject jsurface);
   void SurfaceDestroyed(JNIEnv* env, jobject obj);
 
+  void SetInstance(scoped_ptr<Instance> instance);
+
  private:
   void ReleaseWindow();
 
+  // In principle, the Instance should own the PlatformView, but because our
+  // lifetime is controlled by the Android view hierarchy, we flip around the
+  // ownership and have the Instance owned by Java. We reset this pointer in
+  // |Detach|, which will eventually cause |~PlatformViewAndroid|.
+  scoped_ptr<Instance> instance_;
+
   DISALLOW_COPY_AND_ASSIGN(PlatformViewAndroid);
 };
 
 }  // namespace shell
 }  // namespace sky
 
 #endif  // SKY_SHELL_PLATFORM_VIEW_ANDROID_H_