Delete IsMutable and IsExclusive methods.

webrtc/common_video/include/i420_buffer_pool.h

Index: webrtc/common_video/include/i420_buffer_pool.h
diff --git a/webrtc/common_video/include/i420_buffer_pool.h b/webrtc/common_video/include/i420_buffer_pool.h
index 5c9ab06a097f1afbd0013cc5c6439d7b62890552..834aa4f7c8cbe863f5af4cfdb8dd3ea6538cb975 100644
--- a/webrtc/common_video/include/i420_buffer_pool.h
+++ b/webrtc/common_video/include/i420_buffer_pool.h
@@ -30,14 +30,22 @@ class I420BufferPool {
 
   // Returns a buffer from the pool, or creates a new buffer if no suitable
   // buffer exists in the pool.
-  rtc::scoped_refptr<VideoFrameBuffer> CreateBuffer(int width, int height);
+  rtc::scoped_refptr<I420Buffer> CreateBuffer(int width, int height);
   // Clears buffers_ and detaches the thread checker so that it can be reused
   // later from another thread.
   void Release();
 
  private:
+  class PooledI420Buffer : public webrtc::I420Buffer {
+   public:
+    PooledI420Buffer(int width, int height) : I420Buffer(width, height) {}
+
+    // Underlying refcount access, used by the pool to check exclusive access.
+    virtual bool HasOneRef() const = 0;
+  };
+
   rtc::ThreadChecker thread_checker_;
-  std::list<rtc::scoped_refptr<I420Buffer>> buffers_;
+  std::list<rtc::scoped_refptr<PooledI420Buffer>> buffers_;
   // If true, newly allocated buffers are zero-initialized. Note that recycled
   // buffers are not zero'd before reuse. This is required of buffers used by
   // FFmpeg according to http://crbug.com/390941, which only requires it for the