Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/video/vie_encoder.cc

Index: webrtc/video/vie_encoder.cc
diff --git a/webrtc/video/vie_encoder.cc b/webrtc/video/vie_encoder.cc
index 5722d06c1e651a4961896e49e774e83e9ed5218d..7f18233555c6224c15f84db95a6bbb1e0a5d3f42 100644
--- a/webrtc/video/vie_encoder.cc
+++ b/webrtc/video/vie_encoder.cc
@@ -78,10 +78,10 @@ class ViEEncoder::EncodeTask : public rtc::QueuedTask {
              ViEEncoder* vie_encoder,
              int64_t time_when_posted_in_ms,
              bool log_stats)
-      : vie_encoder_(vie_encoder),
+      : frame_(frame),
+        vie_encoder_(vie_encoder),
         time_when_posted_ms_(time_when_posted_in_ms),
         log_stats_(log_stats) {
-    frame_ = frame;
     ++vie_encoder_->posted_frames_waiting_for_encode_;
   }