VideoFrameBuffer: Make non-const data access explicit

webrtc/common_video/i420_buffer_pool.cc

Index: webrtc/common_video/i420_buffer_pool.cc
diff --git a/webrtc/common_video/i420_buffer_pool.cc b/webrtc/common_video/i420_buffer_pool.cc
index 4b8695824c794ef50f402b4cc2a22e06cc73ded3..cb1f4d4022d49c7fd037fec9861562beb47b7acb 100644
--- a/webrtc/common_video/i420_buffer_pool.cc
+++ b/webrtc/common_video/i420_buffer_pool.cc
@@ -27,13 +27,13 @@ class PooledI420Buffer : public webrtc::VideoFrameBuffer {
   int width() const override { return buffer_->width(); }
   int height() const override { return buffer_->height(); }
   const uint8_t* data(webrtc::PlaneType type) const override {
-    const webrtc::I420Buffer* cbuffer = buffer_.get();
-    return cbuffer->data(type);
+    return buffer_->data(type);
   }
-  uint8_t* data(webrtc::PlaneType type) {
+  uint8_t* MutableData(webrtc::PlaneType type) override {
+    // Make the HasOneRef() check here instead of in |buffer_|, because the pool
+    // also has a reference to |buffer_|.
     DCHECK(HasOneRef());
-    const webrtc::I420Buffer* cbuffer = buffer_.get();
-    return const_cast<uint8_t*>(cbuffer->data(type));
+    return const_cast<uint8_t*>(buffer_->data(type));
   }
   int stride(webrtc::PlaneType type) const override {
     return buffer_->stride(type);