Fix build issue of missing BackingStrategy vtable.

content/common/gpu/media/android_video_decode_accelerator.h

 // Copyright (c) 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 CONTENT_COMMON_GPU_MEDIA_ANDROID_VIDEO_DECODE_ACCELERATOR_H_
 #define CONTENT_COMMON_GPU_MEDIA_ANDROID_VIDEO_DECODE_ACCELERATOR_H_
 
 #include <stdint.h>
 
 #include <list>
@@ skipping 87 matching lines @@
 
     // Whether the pictures produced by this backing strategy are overlayable.
     virtual bool ArePicturesOverlayable() = 0;
 
     // Size may have changed due to resolution change since the last time this
     // PictureBuffer was used. Update the size of the picture buffer to
     // |new_size| and also update any size-dependent state (e.g. size of
     // associated texture). Callers should set the correct GL context prior to
     // calling.
     virtual void UpdatePictureBufferSize(media::PictureBuffer* picture_buffer,
-                                         const gfx::Size& new_size);
+                                         const gfx::Size& new_size) = 0;
   };
 
   AndroidVideoDecodeAccelerator(
       const base::WeakPtr<gpu::gles2::GLES2Decoder> decoder,
       const base::Callback<bool(void)>& make_context_current);
 
   ~AndroidVideoDecodeAccelerator() override;
 
   // media::VideoDecodeAccelerator implementation:
   bool Initialize(const Config& config, Client* client) override;
@@ skipping 215 matching lines @@
 
   // WeakPtrFactory for posting tasks back to |this|.
   base::WeakPtrFactory<AndroidVideoDecodeAccelerator> weak_this_factory_;
 
   friend class AndroidVideoDecodeAcceleratorTest;
 };
 
 }  // namespace content
 
 #endif  // CONTENT_COMMON_GPU_MEDIA_ANDROID_VIDEO_DECODE_ACCELERATOR_H_