Fix bugs in r7291
TBR=reed
Review URL: https://codereview.appspot.com/7129057

git-svn-id: http://skia.googlecode.com/svn/trunk@7292 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index fcaa4cf..98234fa 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -274,8 +274,14 @@
      *    CON: Can't do this with checksums.
      */
     static Checksum get_checksum(const SkBitmap& bitmap) {
-        force_all_opaque(bitmap);
-        return SkBitmapChecksummer::Compute64(bitmap);
+        SkBitmap copy;
+        const SkBitmap* bm = &bitmap;
+        if (bitmap.config() != SkBitmap::kARGB_8888_Config) {
+            bitmap.copyTo(&copy, SkBitmap::kARGB_8888_Config);
+            bm = ©
+        }
+        force_all_opaque(*bm);
+        return SkBitmapChecksummer::Compute64(*bm);
     }
 
     /* since PNG insists on unpremultiplying our alpha, we take no