Add initialization of pixel data in intrapred_test

BUG=aomedia:995

Change-Id: Ic320e5de9b0c7d320b0f6dddce93f1445be61234
diff --git a/test/intrapred_test.cc b/test/intrapred_test.cc
index 6fa1ad5..8ec9a8e 100644
--- a/test/intrapred_test.cc
+++ b/test/intrapred_test.cc
@@ -145,6 +145,8 @@
   DECLARE_ALIGNED(16, uint16_t, above_data[2 * 32 + 32]);
   DECLARE_ALIGNED(16, uint16_t, dst[3 * 32 * 32]);
   DECLARE_ALIGNED(16, uint16_t, ref_dst[3 * 32 * 32]);
+  memset(left_col, 0, sizeof(left_col));
+  memset(above_data, 0, sizeof(above_data));
   RunTest(left_col, above_data, dst, ref_dst);
 }
 
@@ -154,6 +156,8 @@
   DECLARE_ALIGNED(16, uint8_t, above_data[2 * 32 + 32]);
   DECLARE_ALIGNED(16, uint8_t, dst[3 * 32 * 32]);
   DECLARE_ALIGNED(16, uint8_t, ref_dst[3 * 32 * 32]);
+  memset(left_col, 0, sizeof(left_col));
+  memset(above_data, 0, sizeof(above_data));
   RunTest(left_col, above_data, dst, ref_dst);
 }