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/aaclip.cpp b/gm/aaclip.cpp
index b74f6d3..10bfdf4 100644
--- a/gm/aaclip.cpp
+++ b/gm/aaclip.cpp
@@ -36,11 +36,14 @@
     return canvas;
 }
 
+#ifdef SK_DEBUG
 static void GetBitmap(const SkCanvas* canvas, SkBitmap* bm) {
     *bm = canvas->getDevice()->accessBitmap(false);
 }
+#endif
 
 static void compare_canvas(const SkCanvas* a, const SkCanvas* b) {
+#ifdef SK_DEBUG
     SkBitmap bma, bmb;
     GetBitmap(a, &bma);
     GetBitmap(b, &bmb);
@@ -60,6 +63,7 @@
             SkASSERT(0xFF000000 == rowb[x]);
         }
     }
+#endif
 }
 
 static void drawRectAsPath(SkCanvas* canvas, const SkRect& r, const SkPaint& p) {