fix warning from scalar --> int32 conversion

BUG=

Review URL: https://codereview.appspot.com/7065050

git-svn-id: http://skia.googlecode.com/svn/trunk@7061 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/cmykjpeg.cpp b/gm/cmykjpeg.cpp
index 692bc3e..7ac4259 100644
--- a/gm/cmykjpeg.cpp
+++ b/gm/cmykjpeg.cpp
@@ -67,7 +67,7 @@
 void forceLinking();
 
 void forceLinking() {
-    SkImageDecoder *creator = CreateJPEGImageDecoder();
+    SkDEBUGCODE(SkImageDecoder *creator = ) CreateJPEGImageDecoder();
     SkASSERT(creator);
 }