[Chromoting] Add a unit test to verify that the VP8 codec doesn't change color values too much.

remoting/base/decoder_vp8_unittest.cc

Index: remoting/base/decoder_vp8_unittest.cc
diff --git a/remoting/base/decoder_vp8_unittest.cc b/remoting/base/decoder_vp8_unittest.cc
index 4cdb573d66afa8a3f0cc188c20307b142e8cebdf..18a11bfa3eec31ce004516e097f6b50b576886cb 100644
--- a/remoting/base/decoder_vp8_unittest.cc
+++ b/remoting/base/decoder_vp8_unittest.cc
@@ -16,4 +16,10 @@ TEST(DecoderVp8Test, EncodeAndDecode) {
   TestEncoderDecoder(&encoder, &decoder, false);
 }
 
+TEST(DecoderVp8Test, Gradient) {
+  EncoderVp8 encoder;
+  DecoderVp8 decoder;
+  TestEncoderDecoderGradient(&encoder, &decoder, 0.05, 0.01);
+}
+
 }  // namespace remoting