[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..10d1b9f6fa5e4abd608e79106ae7803c21eacd01 100644
--- a/remoting/base/decoder_vp8_unittest.cc
+++ b/remoting/base/decoder_vp8_unittest.cc
@@ -16,4 +16,13 @@ TEST(DecoderVp8Test, EncodeAndDecode) {
   TestEncoderDecoder(&encoder, &decoder, false);
 }
 
+// Check that encoding and decoding a particular frame doesn't change the
+// frame too much. The frame used is a gradient, which does not contain sharp
+// transitions, so encoding lossiness should not be too high.
+TEST(DecoderVp8Test, Gradient) {
+  EncoderVp8 encoder;
+  DecoderVp8 decoder;
+  TestEncoderDecoderGradient(&encoder, &decoder, 0.03, 0.01);
+}
+
 }  // namespace remoting