Update VideoFramePump to pass un-changed frames to encoders.

remoting/codec/codec_test.h

Index: remoting/codec/codec_test.h
diff --git a/remoting/codec/codec_test.h b/remoting/codec/codec_test.h
index 9c9ec7bf83b20c5d8ab2c9e500964f7f1e9b7962..0c143b7791e043a82e3c45bc1e4bab49d03779ef 100644
--- a/remoting/codec/codec_test.h
+++ b/remoting/codec/codec_test.h
@@ -26,6 +26,12 @@ class VideoEncoder;
 // rects match dirty rects.
 void TestVideoEncoder(VideoEncoder* encoder, bool strict);
 
+// Generate test data and test the encoder for a sequence of one "changed"
+// frame followed by one or more "unchanged" frames, and verify that the
+// encoder sends exactly |topoff_frames| of non-empty data for unchanged
+// frames, after which it returns null frames.
+void TestVideoEncoderEmptyFrames(VideoEncoder* encoder, int topoff_frames);
+
 // Generate test data and test the encoder and decoder pair.
 //
 // If |strict| is set to true, this routine will make sure the updated rects