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 de6b9a8a636ed91f912f5f50a802d9a15fadc2be..43be86df2447657a1a08971e26eb3bf11e30e0f0 100644
--- a/webrtc/video/vie_encoder.cc
+++ b/webrtc/video/vie_encoder.cc
@@ -80,10 +80,10 @@ 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_;
   }