Update test code to use I420Buffer when writing pixel data.

webrtc/test/fake_texture_frame.h

Index: webrtc/test/fake_texture_frame.h
diff --git a/webrtc/test/fake_texture_frame.h b/webrtc/test/fake_texture_frame.h
index 23b2954460925b791bf6a1827fcfde334dd11eee..5e7571d87b839d79e7e8b60a8dc3e7d41bc8fda6 100644
--- a/webrtc/test/fake_texture_frame.h
+++ b/webrtc/test/fake_texture_frame.h
@@ -38,8 +38,7 @@ class FakeNativeHandleBuffer : public NativeHandleBuffer {
 
  private:
   rtc::scoped_refptr<VideoFrameBuffer> NativeToI420Buffer() override {
-    rtc::scoped_refptr<VideoFrameBuffer> buffer(
-        I420Buffer::Create(width_, height_));
+    rtc::scoped_refptr<I420Buffer> buffer = I420Buffer::Create(width_, height_);
     int half_height = (height_ + 1) / 2;
     int half_width = (width_ + 1) / 2;
     memset(buffer->MutableDataY(), 0, height_ * width_);