Delete VideoFrame default constructor, and IsZeroSize method.

webrtc/modules/video_coding/generic_encoder.cc

Index: webrtc/modules/video_coding/generic_encoder.cc
diff --git a/webrtc/modules/video_coding/generic_encoder.cc b/webrtc/modules/video_coding/generic_encoder.cc
index 75bdc7c4f39c534b62270b537d23e6bb43559d8a..1786e72ea26009207fe40a94b66e77b9d05099b2 100644
--- a/webrtc/modules/video_coding/generic_encoder.cc
+++ b/webrtc/modules/video_coding/generic_encoder.cc
@@ -123,8 +123,14 @@ int32_t VCMGenericEncoder::SetPeriodicKeyFrames(bool enable) {
 int32_t VCMGenericEncoder::RequestFrame(
     const std::vector<FrameType>& frame_types) {
   RTC_DCHECK_RUNS_SERIALIZED(&race_checker_);
-  VideoFrame image;
-  return encoder_->Encode(image, NULL, &frame_types);
+
+  // TODO(nisse): Used only with internal source. Delete as soon as
+  // that feature is removed. The only implementation I've been able
+  // to find ignores what's in the frame.
+  return encoder_->Encode(VideoFrame(I420Buffer::Create(1, 1),
+                                     kVideoRotation_0, 0),
+                          NULL, &frame_types);
+  return 0;
 }
 
 bool VCMGenericEncoder::InternalSource() const {