Allow larger encoder configurations.

Allow changing colorspace in the encoder and increasing frame size.

Change-Id: I8e7c3b891af29ce420a15beb4f6f9c250245b2bb
diff --git a/test/encode_test_driver.h b/test/encode_test_driver.h
index 765c7d1..7b7dd31 100644
--- a/test/encode_test_driver.h
+++ b/test/encode_test_driver.h
@@ -140,6 +140,12 @@
   }
 #endif
 
+  void Config(const vpx_codec_enc_cfg_t *cfg) {
+    const vpx_codec_err_t res = vpx_codec_enc_config_set(&encoder_, cfg);
+    ASSERT_EQ(VPX_CODEC_OK, res) << EncoderError();
+    cfg_ = *cfg;
+  }
+
   void set_deadline(unsigned long deadline) {
     deadline_ = deadline;
   }