Enable tests using WebM files only if webm_io is enabled

There are a few tests which read/write directly to/from WebM files. They should
be disabled when --disable-webm-io is passed.

Change-Id: Ibac4732e27c66da33082151ba6e6993eaa9a1efd
diff --git a/test/test_vector_test.cc b/test/test_vector_test.cc
index 9ba18da..1f294f2 100644
--- a/test/test_vector_test.cc
+++ b/test/test_vector_test.cc
@@ -12,13 +12,16 @@
 #include <cstdlib>
 #include <string>
 #include "third_party/googletest/src/include/gtest/gtest.h"
+#include "./vpx_config.h"
 #include "test/codec_factory.h"
 #include "test/decode_test_driver.h"
 #include "test/ivf_video_source.h"
 #include "test/md5_helper.h"
 #include "test/test_vectors.h"
 #include "test/util.h"
+#if CONFIG_WEBM_IO
 #include "test/webm_video_source.h"
+#endif
 #include "vpx_mem/vpx_mem.h"
 
 namespace {
@@ -75,7 +78,13 @@
   if (filename.substr(filename.length() - 3, 3) == "ivf") {
     video = new libvpx_test::IVFVideoSource(filename);
   } else if (filename.substr(filename.length() - 4, 4) == "webm") {
+#if CONFIG_WEBM_IO
     video = new libvpx_test::WebMVideoSource(filename);
+#else
+    fprintf(stderr, "WebM IO is disabled, skipping test vector %s\n",
+            filename.c_str());
+    return;
+#endif
   }
   video->Init();