Validate error checking code in decoder.

This patch adds a mechanism for insuring error checking on invalid files
by creating a unit test that runs the decoder and tests that the error
code matches what's expected on each frame in the decoder.

Disabled for now as this unit test will segfault with existing code.

Change-Id: I896f9686d9ebcbf027426933adfbea7b8c5d956e

test/decode_test_driver.h

@@ -114,6 +114,14 @@ class DecoderTest {
   virtual void PreDecodeFrameHook(const CompressedVideoSource& video,
                                   Decoder *decoder) {}
 
+  // Hook to be called to handle decode result. Return true to continue.
+  virtual bool HandleDecodeResult(const vpx_codec_err_t res_dec,
+                                  const CompressedVideoSource& /* video */,
+                                  Decoder *decoder) {
+    EXPECT_EQ(VPX_CODEC_OK, res_dec) << decoder->DecodeError();
+    return VPX_CODEC_OK == res_dec;
+  }
+
   // Hook to be called on every decompressed frame.
   virtual void DecompressedFrameHook(const vpx_image_t& img,
                                      const unsigned int frame_number) {}