Change VCMFrameBuffer and VCMEncodedFrame to use rotation from base class EncodedImage.

BUG=webrtc:5687

Review-Url: https://codereview.webrtc.org/2037633002
Cr-Commit-Position: refs/heads/master@{#13376}
diff --git a/webrtc/modules/video_coding/encoded_frame.h b/webrtc/modules/video_coding/encoded_frame.h
index 9034200..953ab36 100644
--- a/webrtc/modules/video_coding/encoded_frame.h
+++ b/webrtc/modules/video_coding/encoded_frame.h
@@ -75,7 +75,7 @@
   /**
   *   Get frame rotation
   */
-  VideoRotation rotation() const { return _rotation; }
+  VideoRotation rotation() const { return rotation_; }
   /**
   *   True if this frame is complete, false otherwise
   */
@@ -119,7 +119,6 @@
   CodecSpecificInfo _codecSpecificInfo;
   webrtc::VideoCodecType _codec;
   RTPFragmentationHeader _fragmentation;
-  VideoRotation _rotation;
 
   // Video rotation is only set along with the last packet for each frame
   // (same as marker bit). This |_rotation_set| is only for debugging purpose