Cast variance reference output

The larger internal variables are required for the intermediates
but RoundHighBitDepth brings them down to uint32_t/unsigned int.

Fixes type warnings in visual studio.

Change-Id: I48d35284d6cbde330ccdc1f46b6215a645d5eb00

test/variance_test.cc

diff --git a/test/variance_test.cc b/test/variance_test.cc
index e45d90f..78657d9 100644
--- a/test/variance_test.cc
+++ b/test/variance_test.cc
@@ -96,8 +96,8 @@
     }
   }
   RoundHighBitDepth(bit_depth, &se, &sse);
-  *sse_ptr = sse;
-  return sse - (((int64_t) se * se) >> (l2w + l2h));
+  *sse_ptr = (uint32_t) sse;
+  return (unsigned int) (sse - (((int64_t) se * se) >> (l2w + l2h)));
 }
 
 static unsigned int subpel_variance_ref(const uint8_t *ref, const uint8_t *src,
@@ -142,8 +142,8 @@
     }
   }
   RoundHighBitDepth(bit_depth, &se, &sse);
-  *sse_ptr = sse;
-  return sse - (((int64_t) se * se) >> (l2w + l2h));
+  *sse_ptr = (unsigned int) sse;
+  return (unsigned int) (sse - (((int64_t) se * se) >> (l2w + l2h)));
 }
 
 typedef unsigned int (*SumOfSquaresFunction)(const int16_t *src);
@@ -510,8 +510,8 @@
     }
   }
   RoundHighBitDepth(bit_depth, &se, &sse);
-  *sse_ptr = sse;
-  return sse - (((int64_t) se * se) >> (l2w + l2h));
+  *sse_ptr = (unsigned int) sse;
+  return (unsigned int) (sse - (((int64_t) se * se) >> (l2w + l2h)));
 }
 
 template<typename SubpelVarianceFunctionType>