Make the C++ PlatformViewportAndroid's dtor call the Java PVA's destroy() method.

services/native_viewport/platform_viewport_android.h

 // Copyright 2013 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 SERVICES_NATIVE_VIEWPORT_PLATFORM_VIEWPORT_ANDROID_H_
 #define SERVICES_NATIVE_VIEWPORT_PLATFORM_VIEWPORT_ANDROID_H_
 
 #include "base/android/jni_weak_ref.h"
-#include "base/android/scoped_java_ref.h"
 #include "base/macros.h"
 #include "base/memory/weak_ptr.h"
 #include "services/native_viewport/platform_viewport.h"
 #include "ui/events/event_constants.h"
 #include "ui/gfx/rect.h"
 #include "ui/gfx/sequential_id_generator.h"
 #include "ui/gfx/size.h"
 
 namespace gpu {
 class GLInProcessContext;
@@ skipping 41 matching lines @@
   // Overridden from PlatformViewport:
   virtual void Init(const gfx::Rect& bounds) override;
   virtual void Show() override;
   virtual void Hide() override;
   virtual void Close() override;
   virtual gfx::Size GetSize() override;
   virtual void SetBounds(const gfx::Rect& bounds) override;
 
   void ReleaseWindow();
 
-  Delegate* delegate_;
+  Delegate* const delegate_;
+  JavaObjectWeakGlobalRef java_platform_viewport_android_;
   ANativeWindow* window_;
   mojo::ViewportMetricsPtr metrics_;
   ui::SequentialIDGenerator id_generator_;
 
   base::WeakPtrFactory<PlatformViewportAndroid> weak_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(PlatformViewportAndroid);
 };
 
 }  // namespace native_viewport
 
 #endif  // SERVICES_NATIVE_VIEWPORT_PLATFORM_VIEWPORT_ANDROID_H_