scaling from 1x1 will cause dx/dy to be 0. This was confusing the specialized…

scaling from 1x1 will cause dx/dy to be 0.  This was confusing the specialized scalers into calling the wrong function.
BUG=none
TEST=none
R=johannkoenig@google.com, noahric@chromium.org

Review URL: https://webrtc-codereview.appspot.com/1591004

git-svn-id: http://libyuv.googlecode.com/svn/trunk@713 16f28f9a-4ce2-e073-06de-1de4eb20be90

README.chromium

 Name: libyuv
 URL: http://code.google.com/p/libyuv/
-Version: 712
+Version: 713
 License: BSD
 License File: LICENSE
 

include/libyuv/version.h

@@ -11,6 +11,6 @@
 #ifndef INCLUDE_LIBYUV_VERSION_H_  // NOLINT
 #define INCLUDE_LIBYUV_VERSION_H_
 
-#define LIBYUV_VERSION 712
+#define LIBYUV_VERSION 713
 
 #endif  // INCLUDE_LIBYUV_VERSION_H_  NOLINT

source/scale_argb.cc

@@ -1120,7 +1120,7 @@ static void ScaleARGB(const uint8* src, int src_stride,
   }
 
   // Special case for integer step values.
-  if (((dx | dy) & 0xffff) == 0) {
+  if (((dx | dy) & 0xffff) == 0 && dx && dy) {
     // Optimized even scale down. ie 2, 4, 6, 8, 10x.
     if (!(dx & 0x10000) && !(dy & 0x10000)) {
       if ((dx >> 16) == 2) {