Merge "y4m_test: fix segfault if test files are missing"

test/y4m_test.cc

@@ -140,7 +140,7 @@ INSTANTIATE_TEST_CASE_P(C, Y4mVideoSourceTest,
 class Y4mVideoWriteTest
     : public Y4mVideoSourceTest {
  protected:
-  Y4mVideoWriteTest() {}
+  Y4mVideoWriteTest() : tmpfile_(NULL) {}
 
   virtual ~Y4mVideoWriteTest() {
     delete tmpfile_;